Fix API breakage checker configuration

Author: DougGregor

.github/workflows/pull_request.yml

@@ -12,7 +12,7 @@ jobs:
     name: Soundness
     uses: swiftlang/github-workflows/.github/workflows/soundness.yml@main
     with:
-      api_breakage_check_allowlist_path: "Release Notes/api-breakages.txt"
+      api_breakage_check_allowlist_path: "api-breakages.txt"
       docs_check_additional_arguments: "--disable-parameters-and-returns-validation"
   verify_source_code:
     name: Validate generated code