Merge branch '6.4' into 7.2

* 6.4:
  remove invalid redirection entry

Author: javiereguiluz

_build/redirection_map

@@ -575,7 +575,6 @@
 /doctrine/reverse_engineering /doctrine#doctrine-adding-mapping
 /components/serializer /serializer
 /serializer/custom_encoder /serializer/encoders#serializer-custom-encoder
-/components/string /string
 /form/button_based_validation /form/validation_groups
 /form/data_based_validation /form/validation_groups
 /form/validation_group_service_resolver /form/validation_groups