minor fix - removed redundant data

IS/Lab/Lab6/elgamal_schnorr.py

@@ -71,9 +71,8 @@ def schnorr_verify(message: bytes, signature: Tuple[int, int], params: Tuple[int
 
 def demo() -> None:
     print("Lab6: ElGamal (encrypt/decrypt) and Schnorr (sign/verify) demo")
-    default_msg = os.environ.get("LAB6_MESSAGE", "Test message for Lab6")
     try:
-        user_msg = input(f"Enter plaintext [{default_msg}]: ").strip()
+        user_msg = input(f"Enter plaintext: ").strip()
     except EOFError:
         user_msg = ""
     message = (user_msg or default_msg).encode()