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It was part of the old invalidations implementation, and not used
anymore.
This was the last reference from sync to third_party/cacheinvalidation,
so all references to that are also removed from BUILD.gn and DEPS
files.

Bug: 1099672
Change-Id: I3491fa1cea04d0deebe68988cd3af5a5a4da1afb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2270182
Commit-Queue: Mikel Astiz <mastiz@chromium.org>
Auto-Submit: Marc Treib <treib@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#783025}