pmaports.cfg: require pmbootstrap 1.2.0

The new version changed the way firmware is written to SD cards, see:
https://postmarketos.org/deviceinfo

pmaports.cfg

@@ -3,7 +3,7 @@
 # - "version" gets compared with "pmb.config.pmaports_min_version"
 # - "pmbootstrap_min_version" gets compared with "pmb.config.version"
 version=1
-pmbootstrap_min_version=1.1.0
+pmbootstrap_min_version=1.2.0
 branch_pmos=master
 # Compatible branch from Alpine's aports repository
 branch_alpine=edge