message: Remove ubuntu1604 from presubmit.yml
  * Remove ubuntu1604 from presubmit.yml
  Ubuntu 16.04 is end-of-life, we're going to remove it from Bazel CI.
  If you like you can add testing on `ubuntu2004` platform which we also support.
  * Add ubuntu2004 to presubmit.yml
diff: ---
  buildifier: latest
  platforms:
  - ubuntu1604:
  + ubuntu1804:
  build_targets:
  - - "..."
  + - "//..."
  test_targets:
  - - "..."
  - ubuntu1804:
  + - "//..."
  + ubuntu2004:
  build_targets:
  - - "..."
  + - "//..."
  test_targets:
  - - "..."
  + - "//..."
  macos:
  build_targets:
  - - "..."
  + - "//..."
  test_targets:
  - - "..."
  + - "//..."
  