Fix type casting in PluginSpec for ConfigScope [ci fast] (#6469)

Replace unsafe cast with explicit type checking and casting to ensure
type safety when loading ConfigScope extension points. This prevents
potential ClassCastException when loading classes that may not be
ConfigScope implementations.

Signed-off-by: Paolo Di Tommaso <paolo.ditommaso@gmail.com>

Author: pditommaso

modules/nextflow/src/main/groovy/nextflow/plugin/spec/PluginSpec.groovy

@@ -46,14 +46,14 @@ class PluginSpec {
         final definitions = []
 
         for( final className : extensionPoints ) {
-            final clazz = classLoader.loadClass(className) as Class<? extends ConfigScope>
+            final clazz = classLoader.loadClass(className)
 
             if( ConfigScope.class.isAssignableFrom(clazz) ) {
                 final scopeName = clazz.getAnnotation(ScopeName)?.value()
                 final description = clazz.getAnnotation(Description)?.value()
                 if( !scopeName )
                     continue
-                final node = SchemaNode.Scope.of(clazz, description)
+                final node = SchemaNode.Scope.of((Class<? extends ConfigScope>)clazz, description)
 
                 definitions.add(ConfigSpec.of(node, scopeName))
             }