ci: Enable API breakage checks

Author: euanh

.github/workflows/pull_request.yml

@@ -10,7 +10,6 @@ jobs:
         uses: apple/swift-nio/.github/workflows/soundness.yml@main
         with:
             api_breakage_check_container_image: "swift:6.0-noble"
-            api_breakage_check_enabled: false
             docs_check_container_image: "swift:6.0-noble"
             license_header_check_project_name: "SwiftContainerPlugin"
             shell_check_container_image: "swift:6.0-noble"