Allows lifeboat surgery (#6349)

# About the pull request
Title.

# Explain why it's good for the game
I believe blocking lifeboat surgery was an unintended consequence of
#439. That PR was focused on
blocking vehicle surgery, to which lifeboats are not quite the kind that
was being focused. Allowing lifeboats to support surgery will allow
people mid-flight to get surgery, in addition to making them a slightly
better pre-eject hold spot.

# Changelog
:cl:
balance: Lifeboats now support surgery.
/:cl:

code/game/turfs/open.dm

@@ -999,6 +999,7 @@
 	icon = 'icons/turf/almayer.dmi'
 	icon_state = "plating"
 	allow_construction = FALSE
+	supports_surgery = TRUE
 
 // Elevator floors
 /turf/open/shuttle/elevator