Revert "fixes ghosts being flung by mass drivers"

This reverts commit d304c775d6.

Reverts changes made to mob/observer with the intention of changing mass
driver code instead.

code/modules/mob/dead/observer/observer.dm

@@ -16,7 +16,6 @@ GLOBAL_VAR_INIT(observer_default_invisibility, INVISIBILITY_OBSERVER)
 	canmove = FALSE
 	alpha = 127
 	move_resist = INFINITY	//  don't get pushed around
-	anchored = 1 // don't get moved by mass drivers
 	invisibility = INVISIBILITY_OBSERVER
 	var/can_reenter_corpse
 	var/bootime = FALSE