Update notification shows warning for non-app store app

[MorrisJobke]

• having an app installed, that is not in the appstore or where the appstore doesn't deliver the latest version
• this app has following dependency:

<dependencies>
	<nextcloud min-version="14" max-version="15" />
</dependencies>

• having Nextcloud 14 installed
• change to beta channel to get the update notification for 15
• expected: if the app has max version of 15 at least it is not listed in the section "apps missing updates"
• actual: it is listed in "apps missing updates"

cc @nickvergessen

[nextcloud-bot]

GitMate.io thinks possibly related issues are #4663 (Update with disabled app store), #977 (No Notification of app-Update when Update is incombatible ), #5188 (No update shown), #4018 (App Store not loading), and #5627 (Broken app update notification).