libsecp256k1 v0.6.0 released

[Jonas Nick]

Hi list,

We'd like to announce the release of version 0.6.0 of libsecp256k1:

https://github.com/bitcoin-core/secp256k1/releases/tag/v0.6.0

This release adds a MuSig2 module, adds a significantly more robust method to
clear secrets from the stack, and removes the unused secp256k1_scratch_space
functions.

For the full changelog, see
https://github.com/bitcoin-core/secp256k1/blob/master/CHANGELOG.md