Fix: Use uppercase hex for BIP32 pub prefix consistency

Co-authored-by: richardkiss <5336+richardkiss@users.noreply.github.com>

Author: Copilot

pycoin/symbols/tzec.py

@@ -3,4 +3,4 @@
 network = create_bitcoinish_network(
     symbol="tZEC", network_name="Zcash", subnet_name="testnet",
     wif_prefix_hex="ef", address_prefix_hex="1d25", pay_to_script_prefix_hex="1cba",
-    bip32_prv_prefix_hex="04358394", bip32_pub_prefix_hex="043587cf")
+    bip32_prv_prefix_hex="04358394", bip32_pub_prefix_hex="043587CF")