Fix repository URL in C# project file

csharp/src/Google.Protobuf/Google.Protobuf.csproj

@@ -16,7 +16,7 @@
     <PackageProjectUrl>https://github.com/google/protobuf</PackageProjectUrl>
     <PackageLicenseUrl>https://github.com/google/protobuf/blob/master/LICENSE</PackageLicenseUrl>
     <RepositoryType>git</RepositoryType>
-    <RepositoryUrl>https://github.com/nodatime/nodatime.git</RepositoryUrl>
+    <RepositoryUrl>https://github.com/google/protobuf.git</RepositoryUrl>
     <IncludeSymbols>true</IncludeSymbols>
     <IncludeSource>true</IncludeSource>
   </PropertyGroup>