Update .gitlab-ci.yml file

.gitlab-ci.yml

+stages:
+  - migration
+
+image: registry.gitlab.ics.muni.cz:443/cloud/g2/common-cloud-entities:1.0.2
+
+ostack-project-migration:
+  stage: migration
+  script:
+    - echo ci/project-migrator.py --source-openrc prod-einfra_cz_migrator.sh.inc --destination-openrc g2-prod-brno-einfra_cz_migrator.sh.inc --project-name "${PROJECT_NAME}" --validation-a-source-server-id "${VALIDATION_SERVER_ID}" --ceph-migrator-sshkeyfile "${MIGRATOR_SSH_KEY_FILE}"