community/modemmanager: update to 1.18.4 + make libmm-glib dependency versioned

it was previously possible to install different versions if modemmanager is packaged in a masked repo (@repo syntax)

note version 1.18.4 was released a couple of days ago, but the release thread points at a regression with some udev rules from 1.18.2 so I'd rather not upgrade yet - the fix has already been backported so it'd be an easy patch to apply if we want to, but I've asked if they'll also retag a release so might as well wait for that answer first.

EDIT: patch author says this should only affect openwrt: https://lists.freedesktop.org/archives/modemmanager-devel/2021-December/009024.html I didn't thoroughly check and just trusted him and went for the upgrade, I don't use the rules that have been changed on my device so can't test. If someone has a doubt I can pick the patch up as well.