build(deps): bump protobuf in /docker/build/installers

Bumps [protobuf](https://github.com/protocolbuffers/protobuf) from 3.1 to 5.29.6.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Commits](https://github.com/protocolbuffers/protobuf/commits)

---
updated-dependencies:
- dependency-name: protobuf
  dependency-version: 5.29.6
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

docker/build/installers/py27_requirements.txt

@@ -8,7 +8,7 @@ supervisor
 # Google infras.
 glog
 grpcio-tools == 1.2.0
-protobuf == 3.1
+protobuf == 5.29.6
 python-gflags
 
 # Web utils.

docker/build/installers/py3_requrements.txt

@@ -4,7 +4,7 @@
 
 # Google infras.
 glog
-protobuf == 3.1
+protobuf == 5.29.6
 python-gflags
 
 # Web utils.