This reverts commit 96df9aba.

Reason for revert: Upstream fix landed.

Original change's description:
> Temporarily remove 'errorprone_plugin' from roll_chromium_deps.
>
> This dep was causing the script to fail because it doesn't have HEAD.
>
> Bug: angleproject:5887
> Change-Id: Ib6daabfe2e0b105137784ceb80d4147f0eb71f41
> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2848640
> Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
> Commit-Queue: Yuly Novikov <ynovikov@chromium.org>

Bug: angleproject:5887
Change-Id: Ie31e4c998ce15937086ba9c4d589e0995232ab79
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2848642
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>