update docs

docs/constants-and-vars.rst

@@ -16,7 +16,7 @@ Name                 Type             Value
 ==================== ================ =========================================================
 ``block.coinbase``   ``address``      Current block miner's address
 ``block.difficulty`` ``uint256``      Current block difficulty
-``block.prevrandao`` ``uint256``      Current randomness beacon provided by the beacon chain
+``block.prevrandao`` ``bytes32``      Current randomness beacon provided by the beacon chain
 ``block.number``     ``uint256``      Current block number
 ``block.prevhash``   ``bytes32``      Equivalent to ``blockhash(block.number - 1)``
 ``block.timestamp``  ``uint256``      Current block epoch timestamp
@@ -31,7 +31,7 @@ Name                 Type             Value
 
 .. note::
 
-    ``block.prevrandao`` is an alias for ``block.difficulty``. Since ``block.difficulty`` is considered deprecated according to `EIP-4399 <https://eips.ethereum.org/EIPS/eip-4399>`_ after "The Merge" (Paris hard fork), we recommend using ``block.prevrandao``.
+    ``block.prevrandao`` is an alias for the ``block.difficulty`` opcode. Since ``block.difficulty`` is considered deprecated according to `EIP-4399 <https://eips.ethereum.org/EIPS/eip-4399>`_ after "The Merge" (Paris hard fork), we recommend using ``block.prevrandao``.
 
 .. note::