Update formatting Swift version to main (#51)

This PR changes the image container for the formatting action from 6.2
to main, to get around
swiftlang/swift-format#1081

Author: gjcairo

.github/workflows/pull_request.yml

@@ -13,7 +13,7 @@ jobs:
     uses: swiftlang/github-workflows/.github/workflows/soundness.yml@main
     with:
       api_breakage_check_container_image: "swift:6.2-noble"
-      format_check_container_image: "swift:6.2-noble"
+      format_check_container_image: "swiftlang/swift:nightly-main-noble"  # Needed due to https://github.com/swiftlang/swift-format/issues/1081
       license_header_check_project_name: "Swift HTTP Server"
 
   unit-tests: