Plants no longer have pollen particles when they've died. (#96139)

## About The Pull Request

Plants, after they have died, do not actively pollenate their neighbors
in gameplay. However, they do still have pollen particles. This is
definitely a visual oversight, and an easy fix.

Now, after a planet calls `plantdies`, we remove it's pollen particles.

## Why It's Good For The Game

Improves the visual consistency of hydroponics and better communicates
when the mechanic is working as intended.

## Changelog

🆑
fix: Hydroponics trays will no longer produce pollen particles if the
plant in the tray has died.
/🆑

code/modules/hydroponics/hydroponics.dm

@@ -795,6 +795,7 @@
 	set_pestlevel(0, update_icon = FALSE) // Pests die
 	lastproduce = 0
 	SEND_SIGNAL(src, COMSIG_HYDROTRAY_PLANT_DEATH)
+	remove_shared_particles(/particles/pollen) //We shouldn't look like we're pollenating if we're dead.
 	if(update_icon)
 		update_appearance()