Fix whitespace in ERC777 (#2667)

contracts/token/ERC777/ERC777.sol

@@ -51,7 +51,7 @@ contract ERC777 is Context, IERC777, IERC20 {
     mapping(address => mapping(address => bool)) private _revokedDefaultOperators;
 
     // ERC20-allowances
-    mapping (address => mapping (address => uint256)) private _allowances;
+    mapping(address => mapping(address => uint256)) private _allowances;
 
     /**
      * @dev `defaultOperators` may be an empty array.

contracts/token/ERC777/IERC777Sender.sol

@@ -7,7 +7,7 @@ pragma solidity ^0.8.0;
  *
  * {IERC777} Token holders can be notified of operations performed on their
  * tokens by having a contract implement this interface (contract holders can be
- *  their own implementer) and registering it on the
+ * their own implementer) and registering it on the
  * https://eips.ethereum.org/EIPS/eip-1820[ERC1820 global registry].
  *
  * See {IERC1820Registry} and {ERC1820Implementer}.