Greetings,
What to do first. Determine if the "update" is for the App Center itself, or for one of the installed Apps.
This might be difficult since the downloadable version on the support portal for your board as of today is:
B20.0723.1
You'll have to reconcile the Apps since that varies based on what you have installed.
If it really bothers you, you can uninstall,
restart (important step) and reinstall. See if that helps.
I've been using the same version of the App Center on my Z97 rig for almost 3 yrs. I turned off auto update. Works perfectly.