Updated multi-match-query.asciidoc

Corrected note about which field is boosted in a cross-fields multi_match query.

Relates to #12294

docs/reference/query-dsl/multi-match-query.asciidoc

@@ -304,7 +304,7 @@ That solves one of the two problems. The problem of differing term frequencies
 is solved by _blending_ the term frequencies for all fields in order to even
 out the differences.  In other words, `first_name:smith` will be treated as
 though it has the same weight as `last_name:smith`. (Actually,
-`first_name:smith` is given a tiny advantage over `last_name:smith`, just to
+`last_name:smith` is given a tiny advantage over `first_name:smith`, just to
 make the order of results more stable.)
 
 If you run the above query through the <<search-validate>>, it returns this