Bump protobuf from 3.20.3 to 4.25.8 in /demos/mediapipe/object_detection (#3413)

Bumps [protobuf](https://github.com/protocolbuffers/protobuf) from 3.20.3 to 4.25.8.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/protobuf_release.bzl)
- [Commits](protocolbuffers/protobuf@v3.20.3...v4.25.8)

---
updated-dependencies:
- dependency-name: protobuf
  dependency-version: 4.25.8
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

demos/mediapipe/object_detection/requirements.txt

@@ -1,4 +1,4 @@
-protobuf==3.20.3
+protobuf==4.25.8
 tritonclient[all]==2.45.0
 requests==2.32.4
 grpcio