software/metabase: use default bytes= when generating password

no need to have an exception here, long time ago bytes had an insecure
default, but we changed to make the default secure

software/metabase/buildout.hash.cfg

 [instance-profile]
 filename = instance.cfg.in
-md5sum = 0e109afd93153ecf062ad5e76bc86ea4
+md5sum = 8f5680ceb125f684d510adb78b0d1673

software/metabase/instance.cfg.in

@@ -127,7 +127,6 @@ alias = metabase
 
 [postgresql-password]
 recipe = slapos.cookbook:generate.password
-bytes = 24
 
 [postgresql]
 recipe = slapos.cookbook:postgres