Fix variable

.gitlab-ci.yml

@@ -112,7 +112,7 @@ workflow:
         docker tag "${latest_image_name}" "usgs/${CI_PROJECT_NAME}:${ENVIRONMENT}-latest";
         docker push "usgs/${CI_PROJECT_NAME}:${ENVIRONMENT}-latest";
 
-        if [[ ${CI_COMMIT_REF_SLUG} == "${CI_DEFAULT_BRANCH" ]]; then
+        if [[ ${CI_COMMIT_REF_SLUG} == "${CI_DEFAULT_BRANCH}" ]]; then
           docker tag \
               "usgs/${CI_PROJECT_NAME}:${ENVIRONMENT}-latest" \
               "usgs/${CI_PROJECT_NAME}:latest";