Bump protobuf-net from 3.1.17 to 3.1.26

Bumps [protobuf-net](https://github.com/protobuf-net/protobuf-net) from 3.1.17 to 3.1.26.
- [Release notes](https://github.com/protobuf-net/protobuf-net/releases)
- [Changelog](https://github.com/protobuf-net/protobuf-net/blob/main/docs/releasenotes.md)
- [Commits](https://github.com/protobuf-net/protobuf-net/compare/3.1.17...3.1.26)

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

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

DepotDownloader/DepotDownloader.csproj

@@ -11,7 +11,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="protobuf-net" Version="3.1.17" />
+    <PackageReference Include="protobuf-net" Version="3.1.26" />
     <PackageReference Include="SteamKit2" Version="2.4.1" />
   </ItemGroup>
 </Project>