[bip151] fix typo in HKDF key

Author: jonasschnelli

bip-0151.mediawiki

@@ -39,7 +39,7 @@ Encryption initialization must happen before sending any other messages to the r
 The symmetric encryption cipher keys will be calculated with ECDH/HKDF by sharing the pubkeys of a ephemeral key. Once the ECDH secret is calculated on each side, the symmetric encryption cipher keys must be derived with HKDF [2] after the following specification:
 
 1. HKDF extraction
-<code>PRK = HKDF_EXTRACT(hash=SHA256, salt="bitcoinechd", ikm=ecdh_secret|cipher-type)</code>.
+<code>PRK = HKDF_EXTRACT(hash=SHA256, salt="bitcoinecdh", ikm=ecdh_secret|cipher-type)</code>.
 
 2. Derive Key1
 <code>K_1 = HKDF_EXPAND(prk=PRK, hash=SHA256, info="BitcoinK1", L=32)</code>