Switch to globally available Hetzner instance type

The old cx* Intel instance type was only available in EU data centers. The cpx* AMD type is available in the US and Asia as well.

Author: KingMob

config.cfg

@@ -206,7 +206,7 @@ cloud_providers:
     image: Ubuntu 22.04 Jammy Jellyfish
     arch: x86_64
   hetzner:
-    server_type: cx22
+    server_type: cpx21
     image: ubuntu-22.04
   openstack:
     flavor_ram: ">=512"