musig: add note about missing verification to partial_sign to doc

Author: jonasnick

include/secp256k1_musig.h

@@ -442,6 +442,11 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_musig_nonce_process(
  *  created by calling musig_nonce_gen with that pubkey. Otherwise, the
  *  illegal_callback is called.
  *
+ *  This function does not verify the output partial signature, deviating from
+ *  the BIP 327 specification. It is recommended to verify the output partial
+ *  signature with `secp256k1_musig_partial_sig_verify` to prevent random or
+ *  adversarially provoked computation errors.
+ *
  *  Returns: 0 if the arguments are invalid or the provided secnonce has already
  *           been used for signing, 1 otherwise
  *  Args:         ctx: pointer to a context object