[flow][test] Make autostop test more reliable

Summary:
Example of failure: https://github.com/facebook/flow/actions/runs/12471279769/job/34808008899
We should filter out diagonostics messages since it's irrelevant for this test: we only care that the server has started and can respond to requests. The timing of status message vs diagnostics message is not important.

Changelog: [internal]

Reviewed By: panagosg7

Differential Revision: D67610969

fbshipit-source-id: 9b219b6e91fffbf2682f922eb1722add1b0741b6

newtests/autostop/test.js

@@ -34,7 +34,7 @@ module.exports = (suite(
           {method: 'telemetry/connectionStatus', params: {isConnected: true}},
           ['window/showStatus', 'Flow is ready.'],
         ],
-        [],
+        ['textDocument/publishDiagnostics', '$/cancelRequest'],
       ),
     ]),
   ],