Update ActiveRecord::Associations::CollectionProxy#== documentation

[ci skip]
The current documentation for #== shows an example that demonstrates an
incorrect behaviour. This change updates the example accordingly and adds a note
too.

Co-authored-by: Petrik de Heus <[email protected]>

Author: Alex Barret

activerecord/lib/active_record/associations/collection_proxy.rb

@@ -955,10 +955,13 @@ def scope
       #   person.pets == other
       #   # => true
       #
+      #
+      # Note that unpersisted records can still be seen as equal:
+      #
       #   other = [Pet.new(id: 1), Pet.new(id: 2)]
       #
       #   person.pets == other
-      #   # => false
+      #   # => true
       def ==(other)
         load_target == other
       end