Docs: Fix simple_query_string example

The "&" is not part of the simple_query_string DSL

Closes #10563

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

@@ -107,7 +107,7 @@ should be enabled. It is specified as a `|`-delimited string with the
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 {
     "simple_query_string" : {
-        "query" : "foo | bar  & baz*",
+        "query" : "foo | bar + baz*",
         "flags" : "OR|AND|PREFIX"
     }
 }