Revert "gnome-base: Switch back to gnome-software"

pureos-store is in landing now.

This reverts commit f5836b5c.
4 jobs for pureos/byzantium in 3 minutes and 57 seconds
Status Job ID Name Coverage
  Package
passed #346272
librem5
package-pureos-byzantium

00:00:51

passed #346273
librem5:arm64
package-pureos-byzantium:arm64

00:02:43

 
  Test Package
passed #346274
librem5
autopkgtest-pureos-byzantium-package

00:03:03

passed #346275
librem5
lintian-pureos-byzantium-package

00:00:45