Bot_update - Branch detection fix

Should've been "branches" not "branch"

BUG=

Review URL: https://codereview.chromium.org/1304903007

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/build@296476 0039d316-1c4b-4281-b951-d872f2087c98
1 file changed