[BAZEL] Upgrade grpc and protobuf

[marcalff]

Fixes # (issue)

Changes

Please provide a brief description of the changes here.

• Upgrade grpc to 1.81.1 in MODULE.bazel
• Upgrade protobuf to 33.6 in MODULE.bazel

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[marcalff]

CI failure on mac:

2026-06-16T10:01:38.3480700Z In file included from external/grpc+/src/core/xds/grpc/xds_metadata_parser.cc:33:
2026-06-16T10:01:38.3481830Z external/grpc+/src/core/xds/grpc/xds_common_types_parser.h:27:10: error: module grpc+//src/core:grpc_xds_client does not depend on a module exporting 'envoy/type/v3/percent.upb.h'
2026-06-16T10:01:38.3484150Z    27 | #include "envoy/type/v3/percent.upb.h"
2026-06-16T10:01:38.3485020Z       |          ^
2026-06-16T10:01:38.3485610Z external/grpc+/src/core/xds/grpc/xds_common_types_parser.h:29:10: error: module grpc+//src/core:grpc_xds_client does not depend on a module exporting 'google/protobuf/duration.upb.h'
2026-06-16T10:01:38.3486210Z    29 | #include "google/protobuf/duration.upb.h"
2026-06-16T10:01:38.3486640Z       |          ^
2026-06-16T10:01:38.3487170Z external/grpc+/src/core/xds/grpc/xds_common_types_parser.h:30:10: error: module grpc+//src/core:grpc_xds_client does not depend on a module exporting 'google/protobuf/struct.upb.h'
2026-06-16T10:01:38.3487900Z    30 | #include "google/protobuf/struct.upb.h"
2026-06-16T10:01:38.3488130Z       |          ^
2026-06-16T10:01:38.3488650Z external/grpc+/src/core/xds/grpc/xds_common_types_parser.h:31:10: error: module grpc+//src/core:grpc_xds_client does not depend on a module exporting 'google/protobuf/wrappers.upb.h'
2026-06-16T10:01:38.3489250Z    31 | #include "google/protobuf/wrappers.upb.h"
2026-06-16T10:01:38.3489480Z       |          ^
2026-06-16T10:01:38.3489630Z 4 warnings and 4 errors generated.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.83%. Comparing base (de26178) to head (31e14ee).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4164   +/-   ##
=======================================
  Coverage   82.83%   82.83%           
=======================================
  Files         406      406           
  Lines       16913    16913           
=======================================
  Hits        14009    14009           
  Misses       2904     2904           

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.