fix(calamares): enable all DMs in services-artix, clarify both config dirs are online

services-artix.conf enabled only sddm + greetd, so LY/LightDM/LXDM were
installed but never service-enabled -> TTY at boot instead of login screen.
Enable the full DM set (artix-service only activates the installed one).

Docs: the live-overlay calamares/ and calamares-online/ dirs both serve the
online installer; there is no offline Calamares config. settings_offline.conf
shipped by the branding package is unused - the launcher always overwrites it.

iso-profiles/antergos/live-overlay/etc/calamares-online/modules/services-artix.conf

@@ -20,6 +20,12 @@ services:
     action: "enable"
   - name: "sddm"
     action: "enable"
+  - name: "lightdm"
+    action: "enable"
+  - name: "lxdm"
+    action: "enable"
+  - name: "ly"
+    action: "enable"
   - name: "greetd"
     action: "enable"
   - name: "ntpd"