[ci] Sync backport action code with dotnet/runtime

scripts/ci/actions/backport/index.js

@@ -39,7 +39,7 @@ async function run() {
       console.log(`Verified ${comment_user} is a repo collaborator.`);
     } catch (error) {
       console.log(error);
-      throw new BackportException(`Error: @${comment_user} is not a repo collaborator, backporting is not allowed.`);
+      throw new BackportException(`Error: @${comment_user} is not a repo collaborator, backporting is not allowed. If you're a collaborator please make sure your ${repo_owner} team membership visibility is set to Public on https://github.com/orgs/${repo_owner}/people?query=${comment_user}`);
     }
 
     try { await exec.exec(`git ls-remote --exit-code --heads origin ${target_branch}`) } catch { throw new BackportException(`Error: The specified backport target branch ${target_branch} wasn't found in the repo.`); }