Lurkers don't lose invisibility when bumping into invisible mobs (#3921)

# About the pull request

Lurker don't lose invis when bump into partly visible mobs like cloaked
scout/preds.

# Explain why it's good for the game

More fair.

# Testing Photographs and Procedure
<details>
<summary>Screenshots & Videos</summary>

Outdated

https://github.com/cmss13-devs/cmss13/assets/115417687/58990b87-1cd2-45e0-a1ac-830b07fcdc00


</details>


# Changelog
:cl: ihatethisengine
balance: Lurkers don't lose invisibility when they bump into partly
visible mobs.
/:cl:

code/modules/mob/living/carbon/xenomorph/castes/Lurker.dm

@@ -165,4 +165,9 @@
 	if(!lurker_invisibility_action)
 		return
 
+	var/mob/living/carbon/human/bumped_into = movable_atom
+	if(bumped_into.alpha < 100) //ignore invisible scouts and preds
+		return
+
+	to_chat(bound_xeno, SPAN_XENOHIGHDANGER("You bumped into someone and lost your invisibility!"))
 	lurker_invisibility_action.invisibility_off()