Make `TimelockController` receive function virtual (#5506)

Co-authored-by: Arr00 <13561405+arr00@users.noreply.github.com>
Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>

.changeset/gorgeous-apes-jam.md

@@ -0,0 +1,5 @@
+---
+'openzeppelin-solidity': minor
+---
+
+`TimelockController`: Receive function is now virtual.

contracts/governance/TimelockController.sol

@@ -152,7 +152,7 @@ contract TimelockController is AccessControl, ERC721Holder, ERC1155Holder {
     /**
      * @dev Contract might receive/hold ETH as part of the maintenance process.
      */
-    receive() external payable {}
+    receive() external payable virtual {}
 
     /**
      * @dev See {IERC165-supportsInterface}.