Fixed a typo in the documentation's link.

Author: xordoquy

docs/topics/3.1-announcement.md

@@ -206,4 +206,4 @@ This will either be made as a single 3.2 release, or split across two separate r
 [pagination]: ../api-guide/pagination.md
 [versioning]: ../api-guide/versioning.md
 [internationalization]: internationalization.md
-[customizing-field-mappings]: ../api-guide/serializers.md/#customizing-field-mappings
+[customizing-field-mappings]: ../api-guide/serializers.md#customizing-field-mappings