Shorten every instance of "CHANNEL" to "C" and whisper too

To save a little space in messages, it's getting very cramped

Modules/BonkDetector.lua

@@ -93,7 +93,7 @@ function shared.BonkDetector.Init()
 		end
 		---@type Message
 		local message = {
-			channel = "CHANNEL",
+			channel = "C",
 			data = notifyChannel,
 			message = string.format(shared.L.en.bonkDetected, source, destination, subevent),
 		}
@@ -105,7 +105,7 @@ function shared.BonkDetector.Init()
 		if Heimdall_Data.config.echoToRussian then
 			-- Russian message
 			local ruMessage = {
-				channel = "CHANNEL",
+				channel = "C",
 				data = notifyChannel .. "ru",
 				message = string.format(shared.L.ru.bonkDetected, source, destination, subevent),
 			}