Fix hung bots failure stream.

r183235 changed the category name to builder but didn't update
the ct-failure-stream category.

TBR=leviw@chromium.org

Review URL: https://codereview.chromium.org/625343002

git-svn-id: svn://svn.chromium.org/blink/trunk@183238 bbb929c8-8fbe-4397-9dbb-9b2b20218538