docs wrong for custom_commands (rpc)

[bryanhuntesl]

Steps to reproduce

https://hexdocs.pm/distillery/extensibility/custom_commands.html

release_ctl eval --mfa "Mix.Tasks.MyTask.run/1" --argv -- "$@"

Should be :

release_ctl eval "Mix.Tasks.MyTask.run/1" --argv -- "$@"

Folks are getting mixed up by that, and also applying it incorrectly when attempting to

release_remote_ctl rpc "Mix.Tasks.MyTask.run/1" --argv -- "$@"

[bryanhuntesl]

This is also wrong, distillery understands ..

release_remote_ctl rpc "Mix.Tasks.MyTask.run()"