key: use secp256k1_schnorrsig_sign32 over deprecated secp256k1_schnorrsig_sign

The renaming occured in
https://github.com/bitcoin-core/secp256k1/pull/1089.

src/key.cpp

@@ -288,7 +288,7 @@ bool CKey::SignSchnorr(const uint256& hash, Span<unsigned char> sig, const uint2
         uint256 tweak = XOnlyPubKey(pubkey_bytes).ComputeTapTweakHash(merkle_root->IsNull() ? nullptr : merkle_root);
         if (!secp256k1_keypair_xonly_tweak_add(GetVerifyContext(), &keypair, tweak.data())) return false;
     }
-    bool ret = secp256k1_schnorrsig_sign(secp256k1_context_sign, sig.data(), hash.data(), &keypair, aux.data());
+    bool ret = secp256k1_schnorrsig_sign32(secp256k1_context_sign, sig.data(), hash.data(), &keypair, aux.data());
     if (ret) {
         // Additional verification step to prevent using a potentially corrupted signature
         secp256k1_xonly_pubkey pubkey_verify;