pmaports.cfg: set pmbootstrap_min_version=2.2.0 (MR 4756)

This version includes fixes for pmb_recommends, to be used by package
changes in pmaports.

pmaports.cfg

 # Reference: https://postmarketos.org/pmaports.cfg
 [pmaports]
 version=7
-pmbootstrap_min_version=1.53.0
+pmbootstrap_min_version=2.2.0
 channel=edge
 supported_root_filesystems=btrfs,ext4,f2fs
 supported_firewall=nftables