Refresh grains when the master requests to do so

saltstack/salt#48773 is meanwhile closed,
there was an additional feature added to salt [1] and we face problems
with our mine (which is mostly based on grains). So lets try to remove
this option and see if our mine behaves better after that.

[1] saltstack/salt#57062

salt/minion.sls

@@ -26,7 +26,6 @@ speedup_minion:
           - esxi
         disable_modules:
           - vsphere
-        grains_cache: True
 
 # workaround https://github.com/saltstack/salt/issues/59141
 workaround_minion_race: