update CI matrix

Author: mattpolzin

.github/workflows/tests.yml

@@ -15,7 +15,12 @@ jobs:
         image:
           - swift:5.9-focal
           - swift:5.9-jammy
-          - swift:5.9-amazonlinux2
+          - swift:5.10-focal
+          - swift:5.10-jammy
+          - swift:6.0-focal
+          - swift:6.0-jammy
+          - swift:6.1-focal
+          - swift:6.1-jammy
     container: ${{ matrix.image }}
     steps:
     - name: Checkout code