gitlab-fs-integration: Configure labels to trigger build

Recently released jenkins-job-builder v6.4.0[1] adds support to specify
the labels with which a build can be triggered for GitLab plugin.

[1] https://jenkins-job-builder.readthedocs.io/en/latest/changelog.html#release-6-4-0

jobs/gitlab-fs-integration.yml

@@ -45,6 +45,7 @@
           ci-skip: false
           add-note-merge-request: false
           add-vote-merge-request: false
+          force-build-labels: 'ci/{file_system}'
 
     builders:
     - shell: !include-raw-escape: scripts/common/get-node.sh