journal-upload: drop custom option error handling

journal-upload: drop custom option error handling

The line to set opterr=0 was added in the initial commit in
3d090cc6f34e5970765dd1e7ee5e648a056d180d. But afaict, this never worked as
intended, because ':' must be the first char in optstring given to
getopt_long() for it to return ':' for a missing option value. Since
this wasn't set, getopt_long() would return '?', and the missing value
would be handled as an unknown option:
  $ build/systemd-journal-upload --key
  Unknown option --key.
  $ build/systemd-journal-upload --asdf
  Unknown option --asdf.

Let's just do the standard thing:
  $ build/systemd-journal-upload --key
  build/systemd-journal-upload: option '--key' requires an argument
  $ build/systemd-journal-upload --asdf
  build/systemd-journal-upload: unrecognized option '--asdf'