[Tools] Stop fetching build/scripts/tools/deps2git.

We do not need anything from build/ at all, and this one probably got in
when we moved across milestones.

While here, remove a duplicate entry for
build/third_party/cbuildbot_chromite.
Merge pull request #2025 from rakuco/stop-fetching-build-deps2git

[Tools] Stop fetching build/scripts/tools/deps2git.