Update link in musig2.md

This document contained a link to a MuSig2 draft BIP, which is no longer available. I have updated the link with the link to BIP327 in the bitcoin/bips repository.

Update musig2.md

i've removed the extra spaces and standardized the formatting for this section

Author: Liongrass

docs/musig2.md

@@ -18,10 +18,8 @@ below.
 
 ## References
  * [MuSig2 paper](https://eprint.iacr.org/2020/1261.pdf)
- * [Draft MuSig
-   BIP](https://github.com/jonasnick/bips/blob/musig2/bip-musig2.mediawiki)
- * [MuSig2 implementation discussion in
-   `bitcoind`](https://github.com/bitcoin/bitcoin/issues/23326)
+ * [BIP 327 MuSig](https://github.com/bitcoin/bips/blob/master/bip-0327.mediawiki)
+ * [MuSig2 implementation discussion in `bitcoind`](https://github.com/bitcoin/bitcoin/issues/23326)
 
 ## A note on security