Remove typo and fix variable names

src/database/appservice.rs

@@ -28,9 +28,9 @@ impl Appservice {
     }
 
     /**
-     * Remove a appservice registration
+     * Remove an appservice registration
      * 
-     * id is the name you send to register the service
+     * service_name is the name you send to register the service
      */
     pub fn unregister_appservice(&self, service_name: &str) -> Result<()> {
         self.id_appserviceregistrations.remove(service_name.as_bytes())?;