Merge pull request #4532 from jtattermusch/remove_unused_vsprojects

.../grpc++_unsecure/grpc++_unsecure.vcxproj.filters.template

...projects/grpc++_unsecure/grpc++_unsecure.vcxproj.template

...projects/grpc_cpp_plugin/grpc_cpp_plugin.vcxproj.template

...ts/grpc_csharp_plugin/grpc_csharp_plugin.vcxproj.template

...jective_c_plugin/grpc_objective_c_plugin.vcxproj.template

...ts/grpc_python_plugin/grpc_python_plugin.vcxproj.template

...ojects/grpc_ruby_plugin/grpc_ruby_plugin.vcxproj.template

vsprojects/grpc++_unsecure/grpc++_unsecure.vcxproj

vsprojects/grpc++_unsecure/grpc++_unsecure.vcxproj.filters

vsprojects/grpc/grpc.vcxproj

vsprojects/grpc/grpc.vcxproj.filters

vsprojects/grpc_cpp_plugin/grpc_cpp_plugin.vcxproj

vsprojects/grpc_csharp_plugin/grpc_csharp_plugin.vcxproj

...s/grpc_objective_c_plugin/grpc_objective_c_plugin.vcxproj

vsprojects/grpc_python_plugin/grpc_python_plugin.vcxproj

vsprojects/grpc_ruby_plugin/grpc_ruby_plugin.vcxproj

vsprojects/grpc_unsecure/grpc_unsecure.vcxproj

vsprojects/grpc_unsecure/grpc_unsecure.vcxproj.filters