Bug 1590320 - enable dom/workers/test/test_multi_sharedWorker.html for fission. r=perry

Could not reproduce the test fail locally and on tryserver.
Enable the mochitest dom/workers/test/test_multi_sharedWorker.html for fission

Differential Revision: https://phabricator.services.mozilla.com/D51107

--HG--
extra : moz-landing-system : lando

dom/workers/test/mochitest.ini

@@ -145,7 +145,6 @@ tags = mcb
 [test_location.html]
 [test_longThread.html]
 [test_multi_sharedWorker.html]
-skip-if = fission && debug # Timeouts
 [test_multi_sharedWorker_lifetimes.html]
 [test_navigator.html]
 support-files =