Update account.py fixes sort option

Descending order is `desc`, not `des`.

Author: AndreMiras

etherscan/accounts.py

@@ -45,7 +45,7 @@ def get_transaction_page(self, page=1, offset=10000, sort='asc', internal=False)
 
         sort options:
             'asc' -> ascending order
-            'des' -> descending order
+            'desc' -> descending order
 
         internal options:
             True  -> Gets the internal transactions of a smart contract