gh-action: exclude Swift older than 6.0

Author: ktoso

.github/workflows/pull_request.yml

@@ -9,7 +9,7 @@ jobs:
         name: tests
         uses: swiftlang/github-workflows/.github/workflows/swift_package_test.yml@main
         with:
-          exclude_swift_versions: "[{\"swift_version\": \"5.8\"}]"
+          exclude_swift_versions: "[{\"swift_version\": \"5.8\"}, {\"swift_version\": \"5.9\"}, {\"swift_version\": \"5.10\"}]"
           pre_build_command: "apt-get update -y -q && apt-get install -y -q openjdk-21-jdk make"
           build_command: "make"
           env_vars: |