Bump protobuf from 4.25.3 to 5.26.1

Bumps [protobuf](https://github.com/protocolbuffers/protobuf) from 4.25.3 to 5.26.1.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/protobuf_release.bzl)
- [Commits](protocolbuffers/protobuf@v4.25.3...v5.26.1)

---
updated-dependencies:
- dependency-name: protobuf
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

test_requirements.txt

@@ -1,6 +1,6 @@
 # Requirements to run unit tests. Tests import from
 # generated code.
-protobuf==4.25.3
+protobuf==5.26.1
 pytest==7.4.3
 pytest-asyncio==0.20.3
 grpc-stubs==1.53.0.2