Bug 1588161 - Increase max-run-time for windows ccov devtools tests; r=marco

Avoid very frequent task timeouts.

Differential Revision: https://phabricator.services.mozilla.com/D49291

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

taskcluster/ci/test/mochitest.yml

@@ -191,7 +191,7 @@ mochitest-devtools-chrome:
             default: default
     max-run-time:
         by-test-platform:
-            windows10-64-ccov/debug: 7200
+            windows10-64-ccov/debug: 9000
             macosx.*64-ccov/debug: 9000
             linux64-ccov/debug: 7200
             default: 5400