Use parentheses to avoid warnings during compilation in elixir 1.17

[perzanko]

It resolves this warning reported during compilation:

warning: using map.field notation (without parentheses) to invoke function Fresha.Waitlists.Protobuf.Rpc.V1.RPCService.Service.__rpc_calls__() is deprecated, you must add parentheses instead: remote.function()
  lib/waitlists_rpc/grpc/server.ex:6: (module)
  (elixir 1.17.1) src/elixir_compiler.erl:77: :elixir_compiler.dispatch/4
  (elixir 1.17.1) src/elixir_compiler.erl:52: :elixir_compiler.compile/4
  (elixir 1.17.1) src/elixir_module.erl:427: :elixir_module.eval_form/7
  (elixir 1.17.1) src/elixir_module.erl:129: :elixir_module.compile/7

Compilation failed due to warnings while using the --warnings-as-errors option

[JerzyDziala]

:)