Bump protobuf from 3.20.2 to 4.25.8 in /examples/time-series-serverless

Bumps [protobuf](https://github.com/protocolbuffers/protobuf) from 3.20.2 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@v3.20.2...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]

examples/time-series-serverless/requirements.txt

@@ -1,4 +1,4 @@
 iso8601==0.1.14
 yandexcloud==0.80.0
 ydb==0.0.50.843132462
-protobuf==3.20.2
+protobuf==4.25.8