Update fedora-tier-1-eln pull request pipeline and cleanup old pipelines

.github/workflows/ci.yml

@@ -16,15 +16,9 @@ jobs:
 
     strategy:
       matrix:
-        os: [centos, fedora]
-        tier: [tier-0, tier-1]
+        os: [fedora]
+        tier: [tier-1]
         include:
-        - os: centos
-          version: stream9
-        - os: centos
-          variant: ""
-        - os: centos
-          variant: "-rt"
         - os: fedora
           version: eln