bip375: sync vendored DLEQ code with BIP-374

bip-0375/deps/dleq.py is adapted from the BIP-374 reference code but
predates the change that treats the challenge e as a scalar (#2262).
Reduce the challenge hash mod n and reject proofs with e >= n, so the
copy used by the BIP-375 validator matches the current BIP-374
reference.

bip-0375/deps/dleq.py

@@ -32,7 +32,7 @@ def dleq_challenge(
             + m,
         ),
         "big",
-    )
+    ) % GE.ORDER
 
 
 def dleq_generate_proof(
@@ -72,6 +72,8 @@ def dleq_verify_proof(
         return False
     assert len(proof) == 64
     e = int.from_bytes(proof[:32], "big")
+    if e >= GE.ORDER:
+        return False
     s = int.from_bytes(proof[32:], "big")
     if s >= GE.ORDER:
         return False