Corrects 200+ instances of "it's" where it should've been "its" instead (#85169)

## About The Pull Request

it's - conjunction of "it" and "is"
its - possessive form of "it"

grammar is hard, and there were a lot of places where "it's" was used
where it shouldn't have been. i went and painstakingly searched the
entire repository for these instances, spending a few hours on it. i
completely ignored the changelog archive, and i may have missed some
outliers. most player-facing ones should be corrected, though
## Why It's Good For The Game
proper grammar is good

## Changelog
🆑
spellcheck: Numerous instances of "it's" have been properly replaced
with "its"
/🆑

code/game/objects/structures/shower.dm

@@ -4,7 +4,7 @@
 #define SHOWER_NORMAL_TEMP 300
 #define SHOWER_BOILING "boiling"
 #define SHOWER_BOILING_TEMP 400
-/// The volume of it's internal reagents the shower applies to everything it sprays.
+/// The volume of its internal reagents the shower applies to everything it sprays.
 #define SHOWER_SPRAY_VOLUME 5
 /// How much the volume of the shower's spay reagents are amplified by when it sprays something.
 #define SHOWER_EXPOSURE_MULTIPLIER 2 // Showers effectively double exposed reagents
@@ -49,7 +49,7 @@ GLOBAL_LIST_INIT(shower_mode_descriptions, list(
 	var/reagent_capacity = 200
 	///How many units the shower refills every second.
 	var/refill_rate = 0.5
-	///Does the shower have a water recycler to recollect it's water supply?
+	///Does the shower have a water recycler to recollect its water supply?
 	var/has_water_reclaimer = TRUE
 	///Which mode the shower is operating in.
 	var/mode = SHOWER_MODE_UNTIL_EMPTY