Update .gitlab-ci.yml, remove old files

.gitlab-ci.yml

@@ -34,6 +34,7 @@ pages-devel:
   stage: deploy
   script:
     - echo $EXPORT_PAGES_DIR
+    - rm -r $EXPORT_PAGES_DIR/*
     - mkdir .public
     - cp -r css .public
     - cp -r images .public