Suppress new Style/ReturnNilInPredicateMethodDefinition offenses

Follow up Follow up rubocop/rubocop#11967.

This commit suppresses the following new `Style/ReturnNilInPredicateMethodDefinition` offenses:

```console
$ bundle exec rubocop
(snip)

Offenses:

lib/rubocop/cop/rails/action_controller_flash_before_render.rb:88:11: C: [Corrected] Style/ReturnNilInPredicateMethodDefinition:
Use return false instead of return in the predicate method.
          return unless class_node
          ^^^^^^
lib/rubocop/cop/rails/date.rb:142:11: C: [Corrected] Style/ReturnNilInPredicateMethodDefinition:
Use return false instead of return in the predicate method.
          return unless node.method?(:to_time)
          ^^^^^^
lib/rubocop/cop/rails/dynamic_find_by.rb:77:11: C: [Corrected] Style/ReturnNilInPredicateMethodDefinition:
Use return false instead of return in the predicate method.
          return unless cop_config['AllowedMethods']
          ^^^^^^
lib/rubocop/cop/rails/dynamic_find_by.rb:83:11: C: [Corrected] Style/ReturnNilInPredicateMethodDefinition:
Use return false instead of return in the predicate method.
          return unless cop_config['AllowedReceivers'] && node.receiver
          ^^^^^^
lib/rubocop/cop/rails/dynamic_find_by.rb:91:11: C: [Corrected] Style/ReturnNilInPredicateMethodDefinition:
Use return false instead of return in the predicate method.
          return unless whitelist_config
          ^^^^^^
lib/rubocop/cop/rails/freeze_time.rb:72:11: C: [Corrected] Style/ReturnNilInPredicateMethodDefinition:
Use return false instead of return in the predicate method.
          return if time_argument
          ^^^^^^
lib/rubocop/cop/rails/save_bang.rb:191:11: C: [Corrected] Style/ReturnNilInPredicateMethodDefinition:
Use return false instead of return in the predicate method.
          return unless assignment.referenced?
          ^^^^^^
lib/rubocop/cop/rails/save_bang.rb:301:11: C: [Corrected] Style/ReturnNilInPredicateMethodDefinition:
Use return false instead of return in the predicate method.
          return unless method && (method.def_type? || method.block_type?)
          ^^^^^^

281 files inspected, 8 offenses detected, 8 offenses corrected
```

Author: koic

lib/rubocop/cop/rails/action_controller_flash_before_render.rb

@@ -85,7 +85,7 @@ def followed_by_render?(flash_node)
 
         def inherit_action_controller_base?(node)
           class_node = find_ancestor(node, type: :class)
-          return unless class_node
+          return false unless class_node
 
           action_controller?(class_node)
         end

lib/rubocop/cop/rails/date.rb

@@ -139,7 +139,7 @@ def safe_chain?(node)
         end
 
         def safe_to_time?(node)
-          return unless node.method?(:to_time)
+          return false unless node.method?(:to_time)
 
           if node.receiver.str_type?
             zone_regexp = /([+-][\d:]+|\dZ)\z/

lib/rubocop/cop/rails/dynamic_find_by.rb

@@ -74,21 +74,21 @@ def allowed_invocation?(node)
         end
 
         def allowed_method?(node)
-          return unless cop_config['AllowedMethods']
+          return false unless cop_config['AllowedMethods']
 
           cop_config['AllowedMethods'].include?(node.method_name.to_s)
         end
 
         def allowed_receiver?(node)
-          return unless cop_config['AllowedReceivers'] && node.receiver
+          return false unless cop_config['AllowedReceivers'] && node.receiver
 
           cop_config['AllowedReceivers'].include?(node.receiver.source)
         end
 
         # config option `WhiteList` will be deprecated soon
         def whitelisted?(node)
           whitelist_config = cop_config['Whitelist']
-          return unless whitelist_config
+          return false unless whitelist_config
 
           whitelist_config.include?(node.method_name.to_s)
         end

lib/rubocop/cop/rails/freeze_time.rb

@@ -69,7 +69,7 @@ def current_time_with_convert?(node, method_name)
           return false unless CONVERT_METHODS.include?(method_name)
 
           child_node, child_method_name, time_argument = *node.children
-          return if time_argument
+          return false if time_argument
 
           current_time?(child_node, child_method_name)
         end

lib/rubocop/cop/rails/save_bang.rb

@@ -188,7 +188,7 @@ def right_assignment_node(assignment)
         end
 
         def persisted_referenced?(assignment)
-          return unless assignment.referenced?
+          return false unless assignment.referenced?
 
           assignment.variable.references.any? do |reference|
             call_to_persisted?(reference.node.parent)
@@ -298,7 +298,7 @@ def implicit_return?(node)
 
           node = assignable_node(node)
           method, sibling_index = find_method_with_sibling_index(node.parent)
-          return unless method && (method.def_type? || method.block_type?)
+          return false unless method && (method.def_type? || method.block_type?)
 
           method.children.size == node.sibling_index + sibling_index
         end