[DOCS] Replace mention of string field type with text and keyword

Closes #25713

docs/reference/query-dsl/mlt-query.asciidoc

@@ -111,9 +111,10 @@ analyzes it, usually using the same analyzer at the field, then selects the
 top K terms with highest tf-idf to form a disjunctive query of these terms.
 
 IMPORTANT: The fields on which to perform MLT must be indexed and of type
-`string`. Additionally, when using `like` with documents, either `_source`
-must be enabled or the fields must be `stored` or store `term_vector`. In
-order to speed up analysis, it could help to store term vectors at index time.
+`text` or `keyword``. Additionally, when using `like` with documents, either
+`_source` must be enabled or the fields must be `stored` or store
+`term_vector`. In order to speed up analysis, it could help to store term
+vectors at index time.
 
 For example, if we wish to perform MLT on the "title" and "tags.raw" fields,
 we can explicitly store their `term_vector` at index time. We can still