Dear Maintainer,

When building a software using libgrpc, I stepped into this error
message:

```
CMake Error at /usr/lib/x86_64-linux-gnu/cmake/grpc/gRPCTargets.cmake:195
(message):
  The imported target "gRPC::grpc_cpp_plugin" references the file

     "/usr/bin/grpc_cpp_plugin"

  but this file does not exist.  Possible reasons include:

  * The file was deleted, renamed, or moved to another location.

  * An install or uninstall procedure did not complete successfully.

  * The installation package was faulty and contained

     "/usr/lib/x86_64-linux-gnu/cmake/grpc/gRPCTargets.cmake"

  but not all the files it references.
```

After investigating, this executable is actually shipped by protobuf-
compiler-
grpc so it would make sense to have a recommend relationship between the
two
(or maybe even a dependency)