fix: thoroughly remove fedora Flatpaks, and install unfiltered Flathub

We're now deleting the "fedora" Flatpak repos if they're detected on either the system or user level. All software is crippled in their repos, and less maintained than Flathub, so there's no good reason to have them.

More importantly, we're now also installing the Flathub repo system-wide instead of merely the user-level. This has two important effects:

1. People who opted out of "Third Party Repos" during OS installation will now receive the Flathub repo, to ensure that their system still works properly in that scenario.

2. It gets rid of the "Filter" line in `/var/lib/flatpak/repo/config`, so that Fedora can never reinstate the filtering in the future.

As for why we install Flathub at both the user and system levels: We need both, since the user then gets a nice dropdown menu inside GNOME Software, which lets them switch between system-wide or per-user installation locations.

The "remote" name detection has also been improved, by only printing the raw "name" column, to avoid any risk of false positives.

usr/share/ublue-os/firstboot/yafti.yml

@@ -14,12 +14,14 @@ screens:
     values:
       title: Welcome, Traveler!
       condition:
-        run: flatpak remotes --system | grep fedora
+        run: flatpak remotes --columns=name | grep fedora
       description: |
         We have detected the limited, Fedora-provided Flatpak remote on your system, whose applications are usually missing important codecs and other features. This step will therefore remove all basic Fedora Flatpaks from your system! We will instead switch all core Flatpak applications over to the vastly superior, unfiltered Flathub. If you don't want to do this, simply exit this installer.
       actions:
-        - run: flatpak remote-delete fedora --force
+        - run: flatpak remote-delete --system --force fedora
+        - run: flatpak remote-delete --user --force fedora
         - run: flatpak remove --system --noninteractive --all
+        - run: flatpak remote-add --if-not-exists --system flathub https://flathub.org/repo/flathub.flatpakrepo
         - run: flatpak remote-add --if-not-exists --user flathub https://flathub.org/repo/flathub.flatpakrepo
   applications:
     source: yafti.screen.package