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

* [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)

CHANGELOG.next.asciidoc

@@ -207,6 +207,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Fixed scheduler shutdown issues which would in rare situations cause a panic due to semaphore misuse. {pull}16397[16397]
 - Fixed TCP TLS checks to properly validate hostnames, this broke in 7.x and only worked for IP SANs. {pull}17549[17549]
 - Fix broken seccomp filtering and improve security via `setcap` and `setuid` when running as root on linux in containers. {pull}27878[27878]
+- Log browser `zip_url` download failures as `warn` instead of as `info`. {pull}28440[28440]
 
 *Journalbeat*
 

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 {