fix typo in ERC20's documentation

contracts/token/ERC20/ERC20.sol

@@ -76,7 +76,7 @@ contract ERC20 is Context, IERC20, IERC20Metadata {
      *
      * Tokens usually opt for a value of 18, imitating the relationship between
      * Ether and Wei. This is the value {ERC20} uses, unless this function is
-     * overloaded;
+     * overridden;
      *
      * NOTE: This information is only used for _display_ purposes: it in
      * no way affects any of the arithmetic of the contract, including