Drop old versions because of ubuntu package renames

Author: crclark

.github/workflows/ci.yml

@@ -30,8 +30,6 @@ jobs:
           - "6.3.12"
           - "6.2.20"
           - "6.1.13"
-          - "6.0.18"
-          - "5.2.8"
         fdb-api-version:
           - "520"
           - "600"