Remove the last vestiges of RC4.

We've branched for 53 now, so the admin policy for enabling RC4 has
expired. Remove it completely.

Farewell, RC4. There was a time when you saved us from the beast and
rabid poodles. By luck, you didn't have triskaidekaphobia, unlike our
other friends who chained blocks together. (Boy are they annoying.
It'd be wonderful if we could ditch them someday.)

But you always had your biases, which made it hard to trust you with
secrets. Now we have new friends who do the cha-cha twenty times a
day and learned counting from some French mathematician. We just
don't have room for you anymore.

BUG=375342

Review-Url: https://codereview.chromium.org/2030263002
Cr-Commit-Position: refs/heads/master@{#398044}
10 files changed