Adds time defines to a couple of shooting related delay vars (#93966)

## About The Pull Request

Converted `fire_delay` and `shot_delay` vars to use time defines

## Why It's Good For The Game

Code readability

## Changelog
🆑
code: Converted some gun related variables to use time defines, make an
issue report if anything shoots abnormally fast/slow.
/🆑

code/game/objects/structures/cannons/cannon.dm

@@ -15,7 +15,7 @@
 	var/anchorable_cannon = TRUE
 	var/obj/item/stack/cannonball/loaded_cannonball = null
 	var/charge_ignited = FALSE
-	var/fire_delay = 15
+	var/fire_delay = 1.5 SECONDS
 	var/charge_size = 15
 	var/fire_sound = 'sound/items/weapons/gun/general/cannon.ogg'
 

code/game/objects/structures/cannons/mounted_guns/mounted_gun.dm

@@ -28,9 +28,9 @@
 	///If the gun is currently loaded with its maximum capacity.
 	var/fully_loaded_gun = TRUE
 	///delay in firing the gun after lighting
-	var/fire_delay = 5
+	var/fire_delay = 5 DECISECONDS
 	///Delay between shots
-	var/shot_delay = 3
+	var/shot_delay = 3 DECISECONDS
 	///If the gun shakes the camera when firing
 	var/firing_shakes_camera = TRUE
 	///sound of firing for all but last shot
@@ -111,8 +111,8 @@
 	projectile_type = /obj/projectile/bullet/junk
 	loaded_gun = TRUE
 	fully_loaded_gun = TRUE
-	fire_delay = 3
-	shot_delay = 2
+	fire_delay = 3 DECISECONDS
+	shot_delay = 2 DECISECONDS
 	firing_shakes_camera = FALSE
 
 /obj/structure/mounted_gun/pipe/examine_more(mob/user)
@@ -174,8 +174,8 @@
 	projectile_type = /obj/projectile/bullet/shrapnel
 	loaded_gun = TRUE
 	fully_loaded_gun = TRUE
-	fire_delay = 3
-	shot_delay = 1
+	fire_delay = 3 DECISECONDS
+	shot_delay = 1 DECISECONDS
 	firing_shakes_camera = FALSE
 
 /obj/item/ammo_casing/canister_shot