Provable unspendable taproot internal key

We create an unspendable taproot internal key here
https://github.com/block-core/angor/blob/e4a917aeec95adb035221af5914fbdb5038722da/src/Angor/Shared/ProtocolNew/Scripts/TaprootScriptBuilder.cs#L114

However it is not provably unspendable, this is discussed in the PR bellow.

https://github.com/bitcoin/bips/pull/1746