Bump Google.Protobuf in /sessions/Season-02/0205-ApiPartTwo/src/4_Client (csharpfritz#122)

Bumps [Google.Protobuf](https://github.com/protocolbuffers/protobuf) from 3.13.0 to 3.15.0.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.13.0...v3.15.0)

---
updated-dependencies:
- dependency-name: Google.Protobuf
  dependency-type: direct:production
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

sessions/Season-02/0205-ApiPartTwo/src/4_Client/4_Client.csproj

@@ -7,7 +7,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Google.Protobuf" Version="3.13.0" />
+    <PackageReference Include="Google.Protobuf" Version="3.15.0" />
     <PackageReference Include="Grpc.Net.ClientFactory" Version="2.32.0" />
     <PackageReference Include="Grpc.Tools" Version="2.32.0">
       <PrivateAssets>all</PrivateAssets>