[kbn/es] add context to error message (#24664)

This just tweaks the kbn-es error message to provide more context than just `Not Found`

packages/kbn-es/src/install/snapshot.js

@@ -89,7 +89,7 @@ function downloadFile(url, dest, log) {
         }
 
         if (!res.ok) {
-          return reject(new Error(res.statusText));
+          return reject(new Error(`Unable to download elasticsearch snapshot: ${res.statusText}`));
         }
 
         const stream = fs.createWriteStream(downloadPath);