Update dependency bazelbuild/buildtools to latest version
Update dependency bazelbuild/buildtools to latest version

Included changes:

  - 2b0a1af1a898f92183b9a30872525d9f8332a805 bzl-visibility: allow files in javatest directory import ...
  - 50d1694bd2e8f449dde65a830d595ca5edb3306d When buildifier_test rule is ran with `bazel run`, it wil...

BAZEL_BUILDTOOLS_VERSION_REV_ID: 2b0a1af1a898f92183b9a30872525d9f8332a805
Change-Id: Icad3aa40b26cc29259b19ff16d05fd2359c967f5

google/copybara,google/copybara,google/copybara