Bug 1576025 - Increase chunks for windows ccov browser-chrome; r=intermittent-reviewers,egao

Differential Revision: https://phabricator.services.mozilla.com/D43234

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

taskcluster/ci/test/mochitest.yml

@@ -115,6 +115,7 @@ mochitest-browser-chrome:
             linux.*/debug: 16
             linux64-asan/opt: 16
             macosx.*64/debug: 12
+            windows10-64-ccov/debug: 14
             default: 7
     max-run-time:
         by-test-platform: