Remove the RC4 field trial.

The removal has survived a release cycle without needing the field trial. This
can probably be removed now. The rc4_enabled field in SSLConfig still needs to
remain for a little while longer; the admin policy has a few more release
cycles on it.

BUG=375342

Review URL: https://codereview.chromium.org/1771923002

Cr-Commit-Position: refs/heads/master@{#379628}
1 file changed