Bump Google.Protobuf from 3.27.3 to 3.28.1 in /dotnet-etcd

Bumps [Google.Protobuf](https://github.com/protocolbuffers/protobuf) from 3.27.3 to 3.28.1.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/protobuf_release.bzl)
- [Commits](protocolbuffers/protobuf@v3.27.3...v3.28.1)

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

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

dotnet-etcd/dotnet-etcd.csproj

@@ -48,7 +48,7 @@ Advanced uses take advantage of the consistency guarantees to implement database
 
   <ItemGroup>
     <PackageReference Include="Google.Api.CommonProtos" Version="2.15.0" />
-    <PackageReference Include="Google.Protobuf" Version="3.27.3" />
+    <PackageReference Include="Google.Protobuf" Version="3.28.1" />
     <PackageReference Include="Grpc.Net.Client" Version="2.65.0" />
     <PackageReference Include="Grpc.Tools" Version="2.65.0">
       <PrivateAssets>all</PrivateAssets>