fix: install antergos-next-keyring during basestrap, remove artix-release from target

- Add antergos-next-keyring to basestrap install list so keyring files
  are available in the target early (uses host keyring which already
  trusts the Antergos key)
- Add antergos-next to keyrings list so pacman-key --populate imports
  the Antergos key into the target's keychain
- try_remove artix-release so antergos-release doesn't conflict when
  packages module runs later (replaces= PKGBUILD fix also pushed, but
  this works regardless of rebuild)
- Fix remove() method in basestrap main.py: was missing --root <target>,
  causing removals to operate on the HOST instead of the target

iso-profiles/antergos/live-overlay/etc/calamares/modules/basestrap.conf

@@ -24,9 +24,13 @@ pacman:
         mode: "0o755"
     keyrings:
       - artix
+      - antergos-next
 
 base_init: elogind
 
 operations:
   - install:
     - base
+    - antergos-next-keyring
+  - try_remove:
+    - artix-release