plugins/quectel/mm-broadband-modem-qmi-quectel: ignore carrier revision

Quectel EG25-G QMI modem firmware revisions are not matched with carrier configs. Different VoLTE profiles might be selected by the user causing the carrier config revision to change.

Since fwupd uses this string for firmware updates, it gets confused and thinks the user has an update available.

Moreover, this would make it easier for alternative firmwares to provide their firmware version through an AT command.

@aleksm This is still an RFC as I'm not sure about the consequences this MR may have. AFAIK there are currently no QMI based modems supported in fwupd except for this one.