Revert of Timeout expectation for serviceworker/fetch-mixed-content.html (patchset #1 id:1 of https://codereview.chromium.org/668773003/)

Reason for revert:
Fixed by https://codereview.chromium.org/664343005

Original issue's description:
> Timeout expectation for serviceworker/fetch-mixed-content.html
> 
> Timing out following chromium r300644, but this looks like a test-only
> failure due to invalid cert in the localhost HTTPS server.
> 
> BUG=426047
> TBR=aboxhall@chromium.org,horo@chromium.org
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=184199

TBR=aboxhall@chromium.org,jsbell@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=426047

Review URL: https://codereview.chromium.org/648333003

git-svn-id: svn://svn.chromium.org/blink/trunk@184329 bbb929c8-8fbe-4397-9dbb-9b2b20218538