Fixes movement delay stacking when crossing weeds. (#5332)

# About the pull request
Fixes #2227 . Shadow nerfing warrior and praetorian with this one boys. 

# Explain why it's good for the game

bug bad, and fuck oppressor. 

# Changelog

:cl:
fix: Fixes movement delay stacking on weeds
/:cl:

code/modules/cm_aliens/XenoStructures.dm

@@ -160,13 +160,12 @@
 /obj/effect/alien/resin/sticky/Crossed(atom/movable/AM)
 	. = ..()
 	var/mob/living/carbon/human/H = AM
-	// Wait doesn't this stack slows if you get dragged over it? What's going on here?
 	if(istype(H) && !H.ally_of_hivenumber(hivenumber))
-		H.next_move_slowdown = H.next_move_slowdown + slow_amt
+		H.next_move_slowdown = max(H.next_move_slowdown, slow_amt)
 		return .
 	var/mob/living/carbon/xenomorph/X = AM
 	if(istype(X) && !X.ally_of_hivenumber(hivenumber))
-		X.next_move_slowdown = X.next_move_slowdown + slow_amt
+		X.next_move_slowdown = max(X.next_move_slowdown, slow_amt)
 		return .
 
 /obj/effect/alien/resin/sticky/proc/forsaken_handling()

code/modules/cm_aliens/weeds.dm

@@ -186,7 +186,7 @@
 	SEND_SIGNAL(crossing_mob, COMSIG_MOB_WEED_SLOWDOWN, slowdata, src)
 	var/final_slowdown = slowdata["movement_slowdown"]
 
-	crossing_mob.next_move_slowdown += POSITIVE(final_slowdown)
+	crossing_mob.next_move_slowdown = max(crossing_mob.next_move_slowdown, POSITIVE(final_slowdown))
 
 // Uh oh, we might be dying!
 // I know this is bad proc naming but it was too good to pass on and it's only used in this file anyways