[Heartbeat] Set log level to warn for zip download errors (#28440) (#…

…28446)

* [Heartbeat] Set log level to warn for zip download errors

This was set to Info for no good reason, causing it to not show up in
agent logs.

* changelog

(cherry picked from commit ce0eda1)

Co-authored-by: Andrew Cholakian <andrew@andrewvc.com>

x-pack/heartbeat/monitors/browser/source/zipurl.go

@@ -189,7 +189,7 @@ func retryingZipRequest(method string, z *ZipURLSource) (resp *http.Response, er
 		if err == nil {
 			resp.Body.Close()
 		}
-		logp.Info("attempt to download zip at %s failed: %s, will retry in 1s", z.URL, err)
+		logp.Warn("attempt to download zip at %s failed: %s, will retry in 1s", z.URL, err)
 		time.Sleep(time.Second)
 	}
 	if resp != nil && resp.StatusCode > 300 {