Make page deployment have the correct name

I realized that the online docs haven't update in a few months. I think I tracked it down to this commit.

The issue is that the job that creates the documentation needs to be called pages (see here) for gitlab to know to deploy it.

.gitlab-ci.yml

@@ -230,7 +230,7 @@ docs:
 
 # ------------------- Deploy stage -------------------------------------------
 
-deploy-docs:
+pages:
   stage: deploy
   needs: ["docs", "python-3.9"]
   script: