Do not invalidate OS upgrades in the Updates page

The Updates page resets the OS upgrades state to be available again if
there's a change to the updates, or an app removal, etc.. The reason for
this is that package-based systems need to make sure they have all the
packages downloaded, so this would force the user to download any
missing packages.

As a result, if the user has a downloaded OS upgrade in an ostree system,
and restarts GNOME Software, or removes an app, in this state, the OS
upgrade will show the Download button again, even if offline.

Any OS upgrade invalidation should be done by the plugins related to it
and not by the Updates page, so this patch removes the mentioned code.
Status Job ID Name Coverage
  Build
passed #31501
build-gnome-software

00:07:45