Here are the steps below to fix it this issue:

1. Go to hidden icons section in the task bar (^)
2. Right click on the Citrix icon and choose Advanced Preferences
3. A new text box will appear with Advanced Preferences then click on the section Citrix Workspace Updates
4. Click on the option No, don’t notify me then click the Save button.

That should fix the issue for check for updates in Citrix.