fix base58 typo in bip32 header docs

Author: Lawrence Nahum

include/wally_bip32.h

@@ -231,7 +231,7 @@ WALLY_CORE_API int bip32_key_from_parent_path_alloc(
  * :param hdkey: The extended key.
  * :param flags: BIP32_FLAG_KEY_ Flags indicating which key to serialize. You can not
  *|        serialize a private extended key from a public extended key.
- * :param output: Destination for the resulting key in bas58.
+ * :param output: Destination for the resulting key in base58.
  */
 WALLY_CORE_API int bip32_key_to_base58(
     const struct ext_key *hdkey,