So far, the syntax was `target frame-provider register <cmd-options>
[<run-args>]`. Note the optional `run-args` at the end. They are
completely ignored by the actual command, but the command line parser
still accepts them.
This commit removes them.
This was probably a copy-paste error from `CommandObjectProcessLaunch`
which was probably used as a blue-print for `target frame-provider
register`.
7c832fca53