Add link to field data docs from field data fields

This commit adds a link to the field data docs from the field data
fields docs for completeness.

Closes #17672

docs/reference/search/request/fielddata-fields.asciidoc

@@ -1,7 +1,7 @@
 [[search-request-fielddata-fields]]
 === Field Data Fields
 
-Allows to return the field data representation of a field for each hit, for
+Allows to return the <<fielddata,field data>> representation of a field for each hit, for
 example:
 
 [source,js]