Docs: Missing 1 escape character in example

Closes #10446

docs/reference/query-dsl/queries/query-string-syntax.asciidoc

@@ -273,7 +273,7 @@ of a sub-query:
 If you need to use any of the characters which function as operators in your
 query itself (and not as operators), then you should escape them with
 a leading backslash. For instance, to search for `(1+1)=2`, you would
-need to write your query as `\(1\+1\)=2`.
+need to write your query as `\(1\+1\)\=2`.
 
 The reserved characters are:  `+ - = && || > < ! ( ) { } [ ] ^ " ~ * ? : \ /`