[gnome-books] ci: add explicit deps in the nightly job

[Jordan Petridis <jpetridis src gnome org>]

commit e160041de528c97b5b0ce76f087ec255b74b8b28
Author: Jordan Petridis <jpetridis gnome org>
Date:   Sun Aug 2 14:29:08 2020 +0000

    ci: add explicit deps in the nightly job

 .gitlab-ci.yml | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index d93404a1..1c77abc0 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -22,3 +22,5 @@ flatpak:master:
 
 nightly:
     extends: '.publish_nightly'
+    dependencies: 'flatpak:master'
+    needs: 'flatpak:master'