docs: update document according to the recent update

.gitlab-ci.yml

@@ -73,7 +73,7 @@ build:docs:k8s:
   script:
     - sed -i 's%^CVMFS_HTTP_PROXY=.*%CVMFS_HTTP_PROXY=http://squid-01.ihep.ac.cn:3128%' /etc/cvmfs/default.local
     - for repo in sft.cern.ch cepcsw.ihep.ac.cn; do [ -d "/cvmfs/$repo" ] || mkdir /cvmfs/$repo; sudo mount -t cvmfs $repo /cvmfs/$repo; done
-    - bash ./.build.ci.sh docs
+    - bash build-docs.sh
   artifacts:
     paths:
       - docs/build/html/