fix: sync Bazel version with BCR presubmit (#1163)

The values need to match for BCR.

Author: cgrindel

.bcr/presubmit.yml

@@ -4,7 +4,7 @@ bcr_test_module:
     platform: ["macos"]
     bazel:
       # This needs to exactly match the value used in .bazelversion at the root.
-      - 7.1.2
+      - 7.2.1
   tasks:
     run_tests:
       name: "Run test module"