Make Ownable's initial owner explicit (#4267)

Co-authored-by: Ernesto García <ernestognw@gmail.com>

contracts/access/Ownable.sol

@@ -25,8 +25,8 @@ abstract contract Ownable is Context {
     /**
      * @dev Initializes the contract setting the deployer as the initial owner.
      */
-    constructor() {
-        _transferOwnership(_msgSender());
+    constructor(address initialOwner) {
+        _transferOwnership(initialOwner);
     }
 
     /**