fix: use a consistent buildifier version for CI and pre-commit (#1151)

The CI may be broken because it is using the latest version of
buildifier (`6.1.0`) and the pre-commit hooks are using `6.0.0`. `6.1.0`
added extra sorting, so it is now not enough to just run `pre-commit run
-a buildifier` to fix the errors. I have submitted a PR to update the
pre-commit hooks in
keith/pre-commit-buildifier#14 and until it is
merged and a new version is tagged we should use an older version of the
buildifier to ensure the build is green.

---------

Co-authored-by: Richard Levasseur <[email protected]>

Author: aignas

.bazelci/presubmit.yml

@@ -14,8 +14,9 @@
 
 ---
 buildifier:
-  version: latest
-  # keep this argument in sync with .pre-commit-config.yaml
+  # keep these arguments in sync with .pre-commit-config.yaml
+  # Use a specific version to avoid skew issues when new versions are released.
+  version: 6.0.0
   warnings: "all"
 .minimum_supported_version: &minimum_supported_version
   # For testing minimum supported version.