fix: return error when trying to unregister unknown appservice id

Signed-off-by: strawberry <strawberry@puppygock.gay>

src/service/appservice/mod.rs

@@ -143,7 +143,8 @@ impl Service {
 			.registration_info
 			.write()
 			.await
-			.remove(service_name);
+			.remove(service_name)
+			.ok_or_else(|| crate::Error::AdminCommand("Appservice not found"))?;
 
 		self.db.unregister_appservice(service_name)
 	}