Serverless release pipeline - adjust version key for QA (elastic#192968)

## Summary

This PR adjusts the serverless release pipeline script to use the new
key for QA when reading the version.yaml file.

Note that this is a quick fix to get the pipeline running again. Longer
term, we could have multiple slices of QA, so we should think about how
to prepare the script for that scenario.

.buildkite/scripts/serverless/create_deploy_tag/info_sections/commit_info.ts

@@ -36,7 +36,7 @@ export async function getCurrentQARelease() {
   // @ts-ignore
   const fileContent = Buffer.from(releasesFile.data.content, 'base64').toString('utf8');
 
-  const sha = fileContent.match(`qa: "([a-z0-9]+)"`)?.[1];
+  const sha = fileContent.match(`qa-ds-1: "([a-z0-9]+)"`)?.[1];
 
   if (!sha) {
     throw new Error('Could not find QA hash in current releases file');