CI: ensure testing branch names are properly substituted

.gitlab-ci.yml

@@ -4,8 +4,8 @@ deploy_testing:
         - testing
     script:
         - bash ./prepare-online.sh
-        - mkdir -p /opt/spnati-testing/$CI_COMMIT_REF_NAME
-        - rsync -rltz --delete .public/ /opt/spnati-testing/$CI_COMMIT_REF_NAME
+        - mkdir -p "/opt/spnati-testing/${CI_COMMIT_REF_NAME}"
+        - rsync -rltz --delete .public/ "/opt/spnati-testing/${CI_COMMIT_REF_NAME}"
     when: manual
     environment:
         name: testing/$CI_COMMIT_REF_NAME