Fix 404 handling in detect-previous-failed-tests job

Previously `scripts/pipeline_test_report_builder.rb` would fail with
an exit code of 1 when attempting to retrieve CI artifacts that
returned a 404 error. This was happening because the comparison failed
because `Net::HTTP::Response#code` returns a string, not an integer.

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/367944

scripts/pipeline_test_report_builder.rb

@@ -73,7 +73,7 @@ def failed_builds_for_pipeline(pipeline)
   def test_report_for_build(pipeline, build_id)
     fetch("#{pipeline['web_url']}/tests/suite.json?build_ids[]=#{build_id}")
   rescue Net::HTTPServerException => e
-    raise e unless e.response.code == 404
+    raise e unless e.response.code.to_i == 404
 
     puts "Artifacts not found. They may have expired. Skipping this build."
   end