CI: Block pipeline if QEMU testimage fails

Execution of do_testimage have been stable for a while, so we don't need to
allow it to fail anymore. We should not accept changes that breaks it anymore.

Signed-off-by: Esben Haabendal <esben.haabendal@huawei.com>

.gitlab-ci.yml

@@ -277,7 +277,6 @@ build:
 # Build OpenHarmony images using normal CI runners
 test:
   stage: test
-  allow_failure: true
   needs:
     - job: build
       artifacts: false