Disable bazel-diff if repositories.bzl is changed (#2038)

See
https://github.com/bazelbuild/bazel/pull/23651#issuecomment-2361090763
diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index e80d8b7..ce45ac4 100755
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -588,7 +588,7 @@
 
 # Always run all test targets if any of the paths here are modified by the current commit.
 # Values can be directory paths (with a trailing slash) or file paths.
-DISABLE_BAZEL_DIFF_IF_MODIFIED = (".bazelci/", ".bazelversion", "MODULE.bazel")
+DISABLE_BAZEL_DIFF_IF_MODIFIED = (".bazelci/", ".bazelversion", "MODULE.bazel", "repositories.bzl")
 
 COMMIT_RE = re.compile(r"[0-9a-z]{40}")