MM-53879: Fix duplicate loading of license (#25442)

We take a second stab at fixing the issue. Last time,
we were a bit too aggressive in trying to fix a lot of stuff.

I believe changing the cluster event handler had an edge case
somewhere which caused things to fail. Taking a very conservative
approach this time to only fix what is obviously wrong.

Also tested locally in a HA setup.

https://mattermost.atlassian.net/browse/MM-53879
```release-note
NONE
```

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/platform/service.go

@@ -367,9 +367,7 @@ func (ps *PlatformService) Start(broadcastHooks map[string]BroadcastHook) error
 
 		message := model.NewWebSocketEvent(model.WebsocketEventLicenseChanged, "", "", "", nil, "")
 		message.Add("license", ps.GetSanitizedClientLicense())
-		ps.Go(func() {
-			ps.Publish(message)
-		})
+		ps.Publish(message)
 	})
 	return nil
 }