musig: update to BIP v0.5.1 "Rename ordinary tweaking to plain"

src/modules/musig/musig.md

@@ -23,7 +23,7 @@ Therefore, users of the musig module must take great care to make sure of the fo
 # Key Aggregation and (Taproot) Tweaking
 
 Given a set of public keys, the aggregate public key is computed with `secp256k1_musig_pubkey_agg`.
-A (Taproot) tweak can be added to the resulting public key with `secp256k1_xonly_pubkey_tweak_add` and an ordinary tweak can be added with `secp256k1_ec_pubkey_tweak_add`.
+A (Taproot) tweak can be added to the resulting public key with `secp256k1_xonly_pubkey_tweak_add` and a plain tweak can be added with `secp256k1_ec_pubkey_tweak_add`.
 
 # Signing
 
@@ -32,7 +32,7 @@ Essentially, the protocol proceeds in the following steps:
 
 1. Generate a keypair with `secp256k1_keypair_create` and obtain the xonly public key with `secp256k1_keypair_xonly_pub`.
 2. Call `secp256k1_musig_pubkey_agg` with the xonly pubkeys of all participants.
-3. Optionally add a (Taproot) tweak with `secp256k1_musig_pubkey_xonly_tweak_add` and an ordinary tweak with `secp256k1_musig_pubkey_ec_tweak_add`.
+3. Optionally add a (Taproot) tweak with `secp256k1_musig_pubkey_xonly_tweak_add` and a plain tweak with `secp256k1_musig_pubkey_ec_tweak_add`.
 4. Generate a pair of secret and public nonce with `secp256k1_musig_nonce_gen` and send the public nonce to the other signers.
 5. Someone (not necessarily the signer) aggregates the public nonce with `secp256k1_musig_nonce_agg` and sends it to the signers.
 6. Process the aggregate nonce with `secp256k1_musig_nonce_process`.

src/modules/musig/tests_impl.h

@@ -857,7 +857,7 @@ void musig_tweak_test_helper(const secp256k1_xonly_pubkey* agg_pk, const unsigne
 }
 
 /* Create aggregate public key P[0], tweak multiple times (using xonly and
- * ordinary tweaking) and test signing. */
+ * plain tweaking) and test signing. */
 void musig_tweak_test(secp256k1_scratch_space *scratch) {
     unsigned char sk[2][32];
     secp256k1_xonly_pubkey pk[2];