transient-setup: Only add reformatter to favourites

Previously, on live sessions, com.endlessm.Installer.desktop was both
prepended to the favourites, and to the app grid. This made sense in
Endless OS 4 and older, because an app could be shown in both places.
However, starting from Endless OS 5 (or rather, GNOME 40) an app that is
in the favourites is not shown in the grid. Prepending it to the grid is
not harmless because the logic that reads the grid JSON still reserves
space for it, leaving an empty space on the first page of the grid.

Stop prepending it to the grid.

https://phabricator.endlessm.com/T35104

eos-transient-setup

@@ -32,10 +32,6 @@ from gi.repository import GLib, Gio, OSTree  # noqa: E402
 
 log = logging.getLogger(sys.argv[0])
 
-ICON_GRID_DIR = '/var/lib/eos-image-defaults/icon-grid'
-
-DESKTOP_GRID_ID = 'desktop'
-
 EOS_INSTALLER = 'com.endlessm.Installer.desktop'
 EOS_INSTALLER_PATH = os.path.join('/usr/share/applications', EOS_INSTALLER)
 LOCAL_APPS_DIR = '/usr/local/share/applications'
@@ -134,34 +130,6 @@ def install_installer_desktop_file():
     eos_installer_desktop.save_to_file(LOCAL_DESKTOP_PATH)
 
 
-def prepend_installer_to_icon_grid():
-    """Prepend installer to icon grid."""
-    pattern = os.path.join(ICON_GRID_DIR, 'icon-grid-prepend-*.json')
-    c_path = os.path.join(ICON_GRID_DIR, 'icon-grid-prepend-C.json')
-    paths = glob.glob(pattern)
-    if c_path not in paths:
-        paths.append(c_path)
-
-    for path in paths:
-        try:
-            try:
-                with open(path, 'r') as grid_file:
-                    log.info("reading existing file %s", path)
-                    grid = json.load(fp=grid_file)
-            except FileNotFoundError:
-                grid = {}
-
-            desktop = grid.setdefault(DESKTOP_GRID_ID, [])
-            if EOS_INSTALLER not in desktop:
-                desktop.insert(0, EOS_INSTALLER)
-
-                log.info("Writing %s: %s", path, json.dumps(obj=grid))
-                with open(path, 'w') as grid_file:
-                    json.dump(obj=grid, fp=grid_file)
-        except Exception:
-            log.exception("while processing %s", path)
-
-
 def reduce_ostree_min_free_space():
     '''Don't require any free space on disk when installing apps. On live
     systems, free space is at most half of physical RAM, and running out is not
@@ -200,7 +168,6 @@ def main():
 
         reduce_ostree_min_free_space()
         install_installer_desktop_file()
-        prepend_installer_to_icon_grid()
 
 
 if __name__ == '__main__':