Add codename again

Author: kraih

.github/workflows/linux.yml

@@ -11,14 +11,16 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
+        codename:
+          - buster
         perl-version:
           - '5.16'
           - '5.18'
           - '5.20'
           - '5.22'
           - '5.30'
     container:
-      image: perl:${{ matrix.perl-version }}
+      image: perl:${{ matrix.perl-version }}-${{ matrix.codename }}
     services:
       postgres:
         image: postgres