Fix path separator/capitalization in Windows path

Author: lancemayer

docs/quickstart/csharp.md

@@ -155,7 +155,7 @@ From the `examples/csharp/Helloworld` directory:
 
 ```
 @rem Local nuget cache on Windows is located in %UserProfile%\.nuget\packages
-> %UserProfile%\.nuget\packages\Grpc.Tools.{{ site.data.config.grpc_release_tag | remove_first: "v" }}\tools\windows_x86\protoc.exe -I../../protos --csharp_out Greeter --grpc_out Greeter ../../protos/helloworld.proto --plugin=protoc-gen-grpc=%UserProfile%\.nuget\packages\Grpc.Tools.{{ site.data.config.grpc_release_tag | remove_first: "v" }}\tools\windows_x86\grpc_csharp_plugin.exe
+> %UserProfile%\.nuget\packages\grpc.tools\{{ site.data.config.grpc_release_tag | remove_first: "v" }}\tools\windows_x86\protoc.exe -I../../protos --csharp_out Greeter --grpc_out Greeter ../../protos/helloworld.proto --plugin=protoc-gen-grpc=%UserProfile%\.nuget\packages\grpc.tools\{{ site.data.config.grpc_release_tag | remove_first: "v" }}\tools\windows_x86\grpc_csharp_plugin.exe
 ```
 
 **Linux (or OS X by using macosx_x64 directory)**