pmb.config: set default UI to console

Weston is since long not a good default choice anymore. Switch it to
console which is a (mostly) unopinionated default choice.

Reviewed-by: Oliver Smith <ollieparanoid@postmarketos.org>
Link: https://lists.sr.ht/~postmarketos/pmbootstrap-devel/%3C20230607204449.84020-1-luca@z3ntu.xyz%3E

pmb/config/__init__.py

@@ -134,7 +134,7 @@ defaults = {
     "ssh_keys": False,
     "ssh_key_glob": "~/.ssh/id_*.pub",
     "timezone": "GMT",
-    "ui": "weston",
+    "ui": "console",
     "ui_extras": False,
     "user": "user",
     "work": os.path.expanduser("~") + "/.local/var/pmbootstrap",