Drop a no-longer-reached branch and associated needle

Now both GNOME and KDE do offline updates on all supported
releases, we never see an 'update done' screen any more. This
branch is left over from when the KDE offline update branch was
still conditional on release number.

If we ever implement this test on a desktop that doesn't do
offline updates, we can put this back easily enough.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

needles/kde/desktop_package_tool_update_done-20201110.json

@@ -1,16 +0,0 @@
-{
-  "area": [
-    {
-      "height": 17,
-      "xpos": 656,
-      "ypos": 645,
-      "width": 134,
-      "type": "match"
-    }
-  ],
-  "properties": [],
-  "tags": [
-    "DESKTOP-kde",
-    "desktop_package_tool_update_done"
-  ]
-}

tests/desktop_update_graphical.pm

@@ -130,9 +130,6 @@ sub run {
         assert_and_click 'kde_offline_update_reboot';
         boot_to_login_screen;
     }
-    else {
-        assert_screen 'desktop_package_tool_update_done', 180;
-    }
     # back to console to verify updates
     $self->root_console(tty => 3);
     verify_updated_packages;