Add clarification about the purpose of the generate-tests-* jobs

These jobs are only used to test that the jobs can be generated
and not to generate jobs that will be sent to LAVA. The "real"
generate-tests-* jobs are located in the apertis-image-recipes
repositorty.

Signed-off-by: Dylan Aïssi <dylan.aissi@collabora.com>

.gitlab-ci.yml

@@ -98,6 +98,11 @@ render-pages:
     image_path: weekly/v2024
     image_buildid: "fakebuildid"
 
+# !!!
+# All generate-tests-* jobs defined below are not really used,
+# they are intended to test that the jobs can be generated.
+# !!!
+
 generate-tests-apt-amd64-fixedfunction-uefi:
   extends:
     - .generate-tests-apt