gitlab-ci: Tag lightweight jobs to reduce their latency

Lightweight CI runners have been introduced to run jobs which have low resource consumption and do not need privileged containers to reduce costs and latency, so let's use them.

.gitlab-ci.yml

@@ -3,6 +3,8 @@
 pages:
   image: registry.gitlab.apertis.org/infrastructure/apertis-docker-images/v2021dev3-testcases-builder
   stage: deploy
+  tags:
+    - lightweight
   script:
     - mkdir public
     - BRANCHES="v2019 v2020 v2021dev3"