[DOCS] Fix the terms enum API docs for search_after (#76991)

Author: joegallo

docs/reference/search/terms-enum.asciidoc

@@ -98,8 +98,8 @@ Defaults to false.
 query rewrites to `match_none`.
 
 [[terms-enum-search_after-param]]
-`string`::
+`search_after`::
 (Optional, string)
 The string after which terms in the index should be returned. Allows for a form of
-pagination if the last result from one request is passed as the search_after
+pagination if the last result from one request is passed as the `search_after`
 parameter for a subsequent request.