Emit deprecation warning about inverse_of inference only for valid reflections

That is, if the reflection found is not valid, we don't want to emit the warning
because it's misleading. It says the inverse association could have been automatically
inferred but wasn't because `automatically_invert_plural_associations` is disabled.
However, this is not true, because later on, when we check whether the reflection
is valid, we see it's not, and end up returning `nil`.

Author: rosa

activerecord/lib/active_record/reflection.rb

@@ -708,7 +708,7 @@ def automatic_inverse_of
                 plural_inverse_name = ActiveSupport::Inflector.pluralize(inverse_name)
                 reflection = klass._reflect_on_association(plural_inverse_name)
 
-                if reflection && !active_record.automatically_invert_plural_associations
+                if valid_inverse_reflection?(reflection) && !active_record.automatically_invert_plural_associations
                   ActiveRecord.deprecator.warn(
                     "The `#{active_record.name}##{name}` inverse association could have been automatically" \
                     " inferred as `#{klass.name}##{plural_inverse_name}` but wasn't because `automatically_invert_plural_associations`" \