Limit concurrency of prerelease task (aws#5184)

If a prior action run comples after a subsequent run, the prerelease link will be overwritten by a previous commit

Author: rli

.github/workflows/prerelease.yml

@@ -9,6 +9,9 @@ on:
   push:
     branches: [ main, feature/* ]
 
+concurrency:
+  group: ${{ github.workflow }}${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
 
 jobs:
   generate_artifact_toolkit_standalone: