Revert "gitlab-ci: job must be called 'pages' to deploy to GitLab Pages"

This reverts commit c5daf198.

Turns I was confused here.  Yes, the job has to be called "pages" if the
job is deploying to GitLab Pages.  But in the case of `fdroid nightly`, the
thing that is deploying to GitLab Pages is the .gitlab-ci.yml that is in
the *-nightly repo, which is auto-generated by `fdroid nightly`.

fdroidserver#649

.gitlab-ci.yml

@@ -156,7 +156,7 @@ connected Q default x86_64:
   <<: *kvm-template
 
 
-pages:
+deploy_nightly:
   stage: deploy
   only:
     - master