update README to point to GitLab instead of jenkins

I grepped around and couldn't find instances of gitolite anywhere, so
I guess this should:

Closes: #40004

README.md

@@ -28,10 +28,14 @@ server` or you can perform only the update step by running the
 Deploy your changes to production/staging
 -----------------------------------------
 
-Simply push to git on the master or staging branches, Your changes will shortly
-appear at https://research[-staging].torproject.org/.
+Simply push to git on the HEAD or staging branches. Changes on the
+HEAD branch will be published directly to the main website:
 
-The relevant jenkins jobs are:
+<https://research.torproject.org/>
 
-https://jenkins.torproject.org/job/hugo-website-research/
-https://jenkins.torproject.org/job/hugo-website-research-install/
+The staging branch can be used to proposed Merge Requests which will
+show up as a GitLab pages when built. The URL for the GitLab pages is:
+
+<https://tpo.pages.torproject.org/tpo/web/research/>
+
+The state of the CI pipeline can be found [in GitLab](https://gitlab.torproject.org/tpo/web/research/-/pipelines).