gitlab-integration: Remove already grouped duplicate variants

With [1] all possible share configurations are grouped after their
respective backend file system. So those duplicate entries can be
removed reducing the number of jobs in the matrix.

[1] samba-in-kubernetes/sit-environment#117

jobs/gitlab-fs-integration.yml

@@ -2,7 +2,6 @@
     name: samba_gitlab-fs-integration
     file_system:
       - 'cephfs'
-      - 'cephfs.vfs'
       - 'cephfs.mgr.vfs'
     jobs:
       - 'samba_gitlab-{file_system}-integration'