Fix error message string

Author: hypergonial

discord/commands/context.py

@@ -137,7 +137,7 @@ def respond(self):
         if not self.response.is_done():
             return self.interaction.response.send_message
         else:
-            raise RuntimeError(f"Interaction was already issued a response. Try using {type(self).__name__}.followup() instead.")
+            raise RuntimeError(f"Interaction was already issued a response. Try using {type(self).__name__}.send_followup() instead.")
 
     @property
     def send_followup(self):