log stream widget should query source:iis (#9769)

The log stream widget on this dashboard currently queries "iis" but it should query source:iis. Since there is an OOTB integration pipeline for IIS, any formally recognized IIS logs will have the source:iis facet and will not necessarily have "iis" free text in the message attribute of the log. source:iis is a better query.

iis/assets/dashboards/iis_overview.json

@@ -717,7 +717,7 @@
                 ],
                 "indexes": [],
                 "message_display": "expanded-md",
-                "query": "\"iis\"",
+                "query": "source:iis",
                 "show_date_column": true,
                 "show_message_column": true,
                 "sort": {
@@ -832,4 +832,4 @@
             }
         }
     ]
-}
+}