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/modules/client/client_procs.dm

@@ -490,7 +490,7 @@ GLOBAL_LIST_INIT(blacklisted_builds, list(
 		display_unread_notes(src, time_stamp)
 	qdel(query_last_connected)
 
-	var/cached_player_age = set_client_age_from_db(tdata) //we have to cache this because other shit may change it and we need it's current value now down below.
+	var/cached_player_age = set_client_age_from_db(tdata) //we have to cache this because other shit may change it and we need its current value now down below.
 	if (isnum(cached_player_age) && cached_player_age == -1) //first connection
 		player_age = 0
 	var/nnpa = CONFIG_GET(number/notify_new_player_age)