Specify additional checks to be done during folding

After the folding it is important to check that pipelines in main branches
have run to ensure latest version are published. Make this clear in the
review step.

Signed-off-by: Walter Lozano <walter.lozano@collabora.com>

.gitlab-ci/folding.yml

@@ -61,6 +61,8 @@ manual-review:
 
       − Review and merge the merge requests from the previous step. Pay attention to
         those that were submitted to new branches.
+      - Ensure that pipelines for main branches have run as if not the new version
+        of the packages will not reach OBS/Aptly
       - Wait for all packages to build on OBS. Don’t run the next steps until this
         has happened, otherwise dependency loops will be impossible to automatically
         solve.