[Small model] Explicitly close AsyncGenerator (#704)

src/lib/server/generateFromDefaultEndpoint.ts

@@ -21,6 +21,7 @@ export async function generateFromDefaultEndpoint({
 					generated_text = generated_text.slice(0, -stop.length).trimEnd();
 				}
 			}
+			tokenStream.return();
 			return generated_text;
 		}
 	}