[ews] Do not try to download build product from master

https://bugs.webkit.org/show_bug.cgi?id=271463

Reviewed by Jonathan Bedard.

We stopped uploading archives to build master in 273509@main. So, while downloading
archives, when download from s3 fails, there is no point in trying to fallback to
download from build master.

* Tools/CISupport/ews-build/steps.py:
(DownloadBuiltProduct):

Canonical link: https://commits.webkit.org/276539@main

Tools/CISupport/ews-build/steps.py

@@ -5140,7 +5140,8 @@ class DownloadBuiltProduct(shell.ShellCommand):
     name = 'download-built-product'
     description = ['downloading built product']
     descriptionDone = ['Downloaded built product']
-    flunkOnFailure = False
+    haltOnFailure = True
+    flunkOnFailure = True
 
     def getResultSummary(self):
         if self.results not in [SUCCESS, SKIPPED]: