Update EIP-7702: make chain id u256 (ethereum#9143)

7702: make chain id u256

Author: lightclient

EIPS/eip-7702.md

@@ -52,7 +52,7 @@ The transaction is also considered invalid when any field in an authorization
 tuple cannot fit within the following bounds:
 
 ```python
-assert auth.chain_id < 2**64
+assert auth.chain_id < 2**256
 assert auth.nonce < 2**64
 assert len(auth.address) == 20
 assert auth.y_parity < 2**8