Remove untracked dependency "lib32" from browser_tests.isolate

It isn't build anymore. No idea why. However, trybots started to
fail because of this.

BUG=none
TBR=maruel@chromium.org

Review URL: https://codereview.chromium.org/98233010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240867 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240867