Also test Swift 6.1

Since it was released a while back, we should test on it as well.

Author: ktoso

.github/workflows/pull_request.yml

@@ -21,7 +21,7 @@ jobs:
       fail-fast: true
       matrix:
         # swift_version: ['nightly-main']
-        swift_version: ['6.0.2']
+        swift_version: ['6.0.2', '6.1.0']
         os_version: ['jammy']
         jdk_vendor: ['Corretto']
     container: