Remove more equivalents of the now method from the Painless whitelist.

modules/lang-painless/src/main/resources/org/elasticsearch/painless/java.time.txt

@@ -30,13 +30,7 @@ class Clock -> java.time.Clock extends Object {
   Instant instant()
   long millis()
   Clock offset(Clock,Duration)
-  Clock system(ZoneId)
-  Clock systemDefaultZone()
-  Clock systemUTC()
   Clock tick(Clock,Duration)
-  Clock tickMinutes(ZoneId)
-  Clock tickSeconds(ZoneId)
-  Clock withZone(ZoneId)
 }
 
 class Duration -> java.time.Duration extends Comparable,TemporalAmount,Object {