Speech problems works for Megaphones now (#4008)

# About the pull request

Lisping and other speech problems now work for megaphone

# Explain why it's good for the game

Fixing up oversights of different ways to talk not checking/handling
speech problems

# Testing Photographs and Procedure


![image](https://github.com/cmss13-devs/cmss13/assets/91219575/9f7a031e-75e8-45fd-8824-a86a821dc7c4)

# Changelog
:cl:
fix: Speech problems such as lisping now applies when using megaphone
/:cl:

code/game/objects/items/devices/megaphone.dm

@@ -28,6 +28,11 @@
 	var/message = tgui_input_text(user, "Shout a message?", "Megaphone", multiline = TRUE)
 	if(!message)
 		return
+	// we know user is a human now, so adjust user for this check
+	var/mob/living/carbon/human/humanoid = user
+	if(humanoid.speech_problem_flag)
+		var/list/new_message = humanoid.handle_speech_problems(message)
+		message = new_message[1]
 	message = capitalize(message)
 	log_admin("[key_name(user)] used a megaphone to say: >[message]<")