Retry twice the system, API and unknown failures

Signed-off-by: Rémy Coutable <remy@rymai.me>

.gitlab/ci/global.gitlab-ci.yml

 .dedicated-runner:
   retry:
-    max: 1 # This is confusing but this means "2 runs at max".
+    max: 2 # This is confusing but this means "3 runs at max".
     when:
       - unknown_failure
       - api_failure