gitlab-ci: Drop mkdir

Librem5-devkit-flash-image creates it so let's test that code path as
well.

.gitlab-ci.yml

@@ -47,7 +47,6 @@ test:download:
     - apt-get -y update
     - apt-get -y install $FLASHDEPS
   script:
-    - mkdir download
     - scripts/librem5-devkit-flash-image --skip-flash --skip-cleanup --dir=download/
     - ls -l download/devkit.img download/flash_devkit.lst  download/u-boot-devkit-recovery.imx
     - rm -rf download