literally just hook asay into tgui say (#73212)

## About The Pull Request

pressing f3 now opens asay in tgui say
## Why It's Good For The Game

![john willard gets
banned](https://user-images.githubusercontent.com/12202230/216750445-addb4f3f-0df4-47da-891d-4ef4820a10ab.png)

also fixes double-escaped special characters caused by #72407 and
finally gets rid of the gross regular tgui input popup
## Changelog
🆑
fix: asays are no longer double-escaped
admin: asay now uses tgui say
/🆑

---------

Co-authored-by: Scriptis <scriptis@duck.com>

code/datums/keybinding/admin.dm

@@ -7,18 +7,11 @@
 
 /datum/keybinding/admin/admin_say
 	hotkey_keys = list("F3")
-	name = "admin_say"
+	name = ADMIN_CHANNEL
 	full_name = "Admin say"
 	description = "Talk with other admins."
 	keybind_signal = COMSIG_KB_ADMIN_ASAY_DOWN
 
-/datum/keybinding/admin/admin_say/down(client/user)
-	. = ..()
-	if(.)
-		return
-	user.get_admin_say()
-	return TRUE
-
 /datum/keybinding/admin/admin_ghost
 	hotkey_keys = list("F5")
 	name = "admin_ghost"