Update minitest version

A recent release of minitest removed the dependency on `mutex_m`. `mutex_m` is no longer part of the standard library with Ruby 3.4.

Author: andyundso

test/gem_test.rb

@@ -2,7 +2,7 @@
 require 'test_helper'
 require 'tiny_tds/gem'
 
-class GemTest < MiniTest::Spec
+class GemTest < Minitest::Spec
   gem_root ||= File.expand_path '../..', __FILE__
 
   describe TinyTds::Gem do

test/test_helper.rb

@@ -10,7 +10,7 @@
 TINYTDS_SCHEMAS = ['sqlserver_2017', 'sqlserver_azure'].freeze
 
 module TinyTds
-  class TestCase < MiniTest::Spec
+  class TestCase < Minitest::Spec
 
     class << self
 

tiny_tds.gemspec

@@ -25,7 +25,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'rake', '~> 13.0.0'
   s.add_development_dependency 'rake-compiler', '~> 1.2'
   s.add_development_dependency 'rake-compiler-dock', '~> 1.7.0'
-  s.add_development_dependency 'minitest', '~> 5.14.0'
+  s.add_development_dependency 'minitest', '~> 5'
   s.add_development_dependency 'minitest-reporters', '~> 1.6.1'
   s.add_development_dependency 'connection_pool', '~> 2.2.0'
   s.add_development_dependency 'toxiproxy', '~> 2.0.0'