Fix kubernetes config doc

[coltstrgj]

This member variable is called "client" (not "clients") so spring will fail to populate the values as documented.

Locally I tried:

grpc:
  client:
    my-server:
      address: dns:///my-server-using-client
  clients:
    my-server:
      address: dns:///my-server-using-client-with-s

And confirmed that the address is not populated with an "s" provided.

[ST-DDT]

Nicely spotted!

[coltstrgj]

Thanks for getting to that so fast. Nice project by the way, it's been a huge help.

[ST-DDT]

That is nice to hear ❤️ . Thanks again for your contribution. 👍