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/datums/signals.dm

@@ -4,7 +4,7 @@
  * This sets up a listening relationship such that when the target object emits a signal
  * the source datum this proc is called upon, will receive a callback to the given proctype
  * Use PROC_REF(procname), TYPE_PROC_REF(type,procname) or GLOBAL_PROC_REF(procname) macros to validate the passed in proc at compile time.
- * PROC_REF for procs defined on current type or it's ancestors, TYPE_PROC_REF for procs defined on unrelated type and GLOBAL_PROC_REF for global procs.
+ * PROC_REF for procs defined on current type or its ancestors, TYPE_PROC_REF for procs defined on unrelated type and GLOBAL_PROC_REF for global procs.
  * Return values from procs registered must be a bitfield
  *
  * Arguments: