Bump protobuf from 4.23.1 to 4.25.8 in /samples/polyglot

Bumps [protobuf](https://github.com/protocolbuffers/protobuf) from 4.23.1 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@v4.23.1...v4.25.8)

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

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

Author: dependabot[bot]

samples/polyglot/requirements.txt

@@ -1,4 +1,4 @@
-protobuf==4.23.1
+protobuf==4.25.8
 temporalio==1.16.0
 types-protobuf==4.23.0.1
 typing_extensions==4.5.0