Remove Jenkins from Ref Arch pages (#753)

Author: Pete Emerson

_data/reference-architecture.yml

@@ -33,7 +33,7 @@ infrastructure:
 
   - title: CI server
     description: |
-      Choose from GitHub Actions, CircleCI, GitLab, or Jenkins.
+      Choose from GitHub Actions or CircleCI.
 
   - title: Sample frontend app
     description: |