Update README.md to switch to gitlab runner.

README.md

 [[_TOC_]]
 
-[![Build Status](https://drone.svc.stanford.edu/api/badges/authnz/docker-openldap/status.svg)](https://drone.svc.stanford.edu/authnz/docker-openldap)
+[![pipeline status](https://code.stanford.edu/authnz/docker-openldap/badges/master/pipeline.svg)](https://code.stanford.edu/authnz/docker-openldap/-/commits/master)
 
 # Stanford OpenLDAP in Container
 
 This repository contains instructions on how to build and publish docker-openldap image to
 Google Container Registry.
-
-This repository supports [DroneCI](https://drone.svc.stanford.edu/authnz/docker-openldap).
-
-# Get and setup personal drone token
-
-Drone CLI requires access token to authenticate to a drone server.
-
-You can get your [personal token](https://drone.svc.stanford.edu/account/token),
-and save the token to ${HOME}/.drone-token file.
-
-_NOTE_: Make sure you do not have newline at the end of the token file. You will get authentication failure.
-
-# Turn on the ci job defined in .drone.yml
-
-NOTE: This will setup the hook for CI trigger. It needs to be done only once. You don't
-need to run this if it's been setup already.
-
-```console
-$ make drone-setup
-...
-```
-
-See .drone.yml for build steps and triggers.
-
 # Update OpenLdap image
 
-To upgrade software version and base image, edit build.sh, env.sh to change `OPENLDAP_VERSION`, and edit `.drone.yml` to change tag.
+To upgrade software version and base image, edit build.sh, env.sh to change `OPENLDAP_VERSION`, and edit `.gitlab.yml` to change tag.
 
 If you make changes to the repository, you can test build manually. If the build is successful,
 then commit and push changes to the docker-openldap repository. It will trigger CI/CD to build and upload