Bump Google.Protobuf from 3.15.8 to 3.29.2

Bumps [Google.Protobuf](https://github.com/protocolbuffers/protobuf) from 3.15.8 to 3.29.2.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/protobuf_release.bzl)
- [Commits](protocolbuffers/protobuf@v3.15.8...v3.29.2)

---
updated-dependencies:
- dependency-name: Google.Protobuf
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

Shadowsocks.Protobuf/Shadowsocks.Protobuf.csproj

@@ -5,7 +5,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Google.Protobuf" Version="3.23.4" />
+    <PackageReference Include="Google.Protobuf" Version="3.29.2" />
   </ItemGroup>
 
 </Project>