Install TubeFixer for iOS
TubeFixer for iOS works on iOS 3.0 through 5.1.1 on both the stock app and the App Store app, and it will remove the update nag from the iOS 6 YouTube app.
Install with Cydia
Alternatively you can add the repo
cydia.invoxiplaygames.uk in Cydia and install TubeFixer for iOS from there.
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