Update term-suggest.asciidoc (#86780)

* Update term-suggest.asciidoc

It is really easy to miss the fact, that that's the default setting, since it is not highlighted or called out in anyway

* Apply review suggestion

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Co-authored-by: Abdon Pijpelink <abdon.pijpelink@elastic.co>

docs/reference/search/suggesters/term-suggest.asciidoc

@@ -41,7 +41,7 @@ doesn't take the query into account that is part of request.
     suggested. Three possible values can be specified:
 +
      ** `missing`:  Only provide suggestions for suggest text terms that are
-                    not in the index. This is the default.
+                    not in the index (default).
      ** `popular`:  Only suggest suggestions that occur in more docs than
                     the original suggest text term.
      ** `always`:   Suggest any matching suggestions based on terms in the