[Doc] Correct jdbc url example (#35513)

Adds a missing `?` to separate the url parameters.

docs/reference/sql/endpoints/jdbc.asciidoc

@@ -129,7 +129,7 @@ To put all of it together, the following URL:
 
 ["source","text"]
 ----
-jdbc:es://http://server:3456/timezone=UTC&page.size=250
+jdbc:es://http://server:3456/?timezone=UTC&page.size=250
 ----
 
 Opens up a {es-sql} connection to `server` on port `3456`, setting the JDBC connection timezone to `UTC` and its pagesize to `250` entries.