General maintenance and repair for looping fan sfx (#87453)

## About The Pull Request
closes https://github.com/tgstation/tgstation/issues/87447
Comparison below:
<details>

### Old:


https://github.com/user-attachments/assets/07bab256-bf3b-4442-972c-d03a75a9d7f7


https://github.com/user-attachments/assets/935f54df-1c23-4652-bba0-7345fbe8ddde


https://github.com/user-attachments/assets/61bea6c0-87bd-4027-ad67-243c13e9a166


https://github.com/user-attachments/assets/a0148e09-7f24-406c-a9b3-55cc7c5a49bf

### New:


https://github.com/user-attachments/assets/d3176e85-a768-4343-9cdc-53a0cf202c5f


https://github.com/user-attachments/assets/c4c99a06-eca3-4ab7-a167-2854fa149610


https://github.com/user-attachments/assets/2d46a235-268d-472b-8592-826bbbf59e23


https://github.com/user-attachments/assets/7ba26b21-84da-4959-82ab-96f7885f29d6

</details>

## Why It's Good For The Game

I think it's better
## Changelog
🆑 grungussuss
sound: fan loop sounds have been improved
/🆑

code/datums/looping_sounds/_looping_sound.dm

@@ -4,7 +4,7 @@
 /datum/looping_sound
 	/// (list or soundfile) Since this can be either a list or a single soundfile you can have random sounds. May contain further lists but must contain a soundfile at the end. In a list, path must have also be assigned a value or it will be assigned 0 and not play.
 	var/mid_sounds
-	/// The length of time to wait between playing mid_sounds.
+	/// The length of time to wait between playing mid_sounds. WARNING: Continuously looping sounds like the microwave, grav gen and fan sounds don't work very well with this, just don't set this if you are doing a continuous loop of machinery.
 	var/mid_length
 	/// Amount of time to add/take away from the mid length, randomly
 	var/mid_length_vary = 0

code/datums/looping_sounds/vents.dm

@@ -4,4 +4,3 @@
 	end_sound = 'sound/machines/fan/fan_stop.ogg'
 	end_sound = 1.5 SECONDS
 	mid_sounds = 'sound/machines/fan/fan_loop.ogg'
-	mid_length = 2 SECONDS