Rolling v8/third_party/icu: https://chromium.googlesource.com/chromium/deps/icu/+log/bbdc7d8..20f8ac6

Make references to //third_party/icu relative (Filip Filmar)
https://chromium.googlesource.com/chromium/deps/icu/+/20f8ac6

R=v8-waterfall-sheriff@grotations.appspotmail.com,mtv-sf-v8-sheriff@grotations.appspotmail.com,ftang@chromium.org

Change-Id: I87063f9ec7b4ef8491c43ad8e1902e2741dd0e49
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3886397
Bot-Commit: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Commit-Queue: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#83093}