Fix container image name

Author: stmontgomery

.github/workflows/pull_request.yml

@@ -23,7 +23,7 @@ jobs:
     uses: swiftlang/github-workflows/.github/workflows/soundness.yml@main
     with:
       license_header_check_project_name: "Swift"
-      docs_check_container_image: "swift:nightly-6.2-noble"
+      docs_check_container_image: "swiftlang/swift:nightly-6.2-noble"
       unacceptable_language_check_enabled: false
       format_check_enabled: false
       api_breakage_check_enabled: false