Restructured endless loop definition

I prefer to easily spot an endless loop by not having external variables attached to the loop condition.
Since we never updated `exists` it's a dummy variable that I expect to be updated some where in order to break it.
When that's not the case, it's more clear that it's an endless loop if there's no conditions attached to the loop definition.

archinstall/lib/user_interaction.py

@@ -130,8 +130,7 @@ def ask_for_additional_users(prompt='Any additional users to install (leave blan
 	return users, super_users
 
 def ask_for_a_timezone():
-	exists = False
-	while not exists:
+	while True:
 		timezone = input('Enter a valid timezone (examples: Europe/Stockholm, US/Eastern) or press enter to use UTC: ').strip()
 		if timezone == '':
 			timezone = 'UTC'