[Fleet] bundled packages - use package storage v2 for synthetics (ela…

…stic#146931)

## Summary

Relates to failures seen on
elastic#146823

Synthetics package is just published into package storage v2, so it
requires to add an exception as it was done for the APM package.

(cherry picked from commit e76171c)

src/dev/build/tasks/bundle_fleet_packages.ts

@@ -70,8 +70,12 @@ export const BundleFleetPackages: Task = {
         const archivePath = `${fleetPackage.name}-${versionToWrite}.zip`;
         let archiveUrl = `${eprUrl}/epr/${fleetPackage.name}/${fleetPackage.name}-${fleetPackage.version}.zip`;
 
-        // Point APM and Endpoint packages to package storage v2
-        if (fleetPackage.name === 'apm' || fleetPackage.name === 'endpoint') {
+        // Point APM, Endpoint and Synthetics packages to package storage v2
+        if (
+          fleetPackage.name === 'apm' ||
+          fleetPackage.name === 'endpoint' ||
+          fleetPackage.name === 'synthetics'
+        ) {
           archiveUrl = `${PACKAGE_STORAGE_V2_URL}/epr/${fleetPackage.name}/${fleetPackage.name}-${fleetPackage.version}.zip`;
         }