fix leftover --runtime-file flag (#66)

Author: Samueru-sama

build.sh

@@ -103,4 +103,4 @@ cd "${TMP_DIR}"
 URUNTIME_PRELOAD=1 appimagetool --comp zstd \
 	--mksquashfs-opt -Xcompression-level --mksquashfs-opt 22 \
 	--mksquashfs-opt -b --mksquashfs-opt 1M \
-	-u "${UPINFO}" "${APP_DIR}" --runtime-file /usr/local/bin/uruntime
+	-u "${UPINFO}" "${APP_DIR}"