Fix bitmax signature encoding
Fix bitmax signature encoding

Same problem as https://github.com/ccxt/ccxt/issues/5229
Same fix as https://github.com/ccxt/ccxt/commit/7b95bb5d2eae3cada5f56a1dee992cb0b8af2f02

ccxt/ccxt,ccxt/ccxt,ccxt/ccxt,ccxt/ccxt,ccxt/ccxt