This was only intended for arguments that were previously accepted after
the script name on the command line. For example, in some previous
versions,

    gjs myapp.js -C myfiles

would pass the -C argument to GJS and hide it from myapp.js. We changed
this some time ago, but kept the behaviour for these arguments while
logging a warning.

However, new arguments should not get this behaviour. I accidentally
implemented it for --profile. Technically it's not backwards compatible
to remove it now, but I think it's OK because nobody would ever have
been able to write

    gjs myapp.js --profile myapp.syscap

without getting a warning stating that they shouldn't do that.