metavideo: add auto_update true

[piijai]

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Update according to issue #170994 (comment)

• Livecheck returns the latest version.
• MetaVideo provides the option to enable automatic updates in the pop-up window, when a new version is available.

Although this cask is not on the list, it matches the criteria of the issue. The app is from the NeededApps and metaimage, gluemotion, snapmotion and photsrevive are also apps from this publisher and are on the list. Please consider adding MetaVideo to the list.

Screenshot:

[khipp]

Thank you, @piijai!