Update doc: match actual compact JSON output

Task-number: QTBUG-36682
Change-Id: I0fca746a7838cce49efc243a242bb9bb7119bd9e
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>

src/corelib/json/qjsondocument.cpp

@@ -331,7 +331,7 @@ QByteArray QJsonDocument::toJson() const
 
     \value Compact Defines a compact output as follows:
         \code
-        {"Array": [true,999,"string"],"Key": "Value","null": null}
+        {"Array":[true,999,"string"],"Key":"Value","null":null}
         \endcode
   */