Don't suggest updating masked flatpaks #2376
Description
Problem
I need to keep an application which introduced a critical bug in newer version (Firefox, for me) pinned at a previous version. I did so via console, running the command flatpak mask. AppCenter still offers to update the package, though.
Proposal
Make AppCenter check if a given package is masked; display if it is, instead of "Update" button.
Prior Art (Optional)
No response