Fix Changelog structure

CHANGELOG.md

 # Changelog
 
 ## Unreleased
+
+* `ERC20Votes`: add a new extension of the `ERC20` token with support for voting snapshots and delegation. This extension is compatible with Compound's `Comp` token interface. ([#2632](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2632))
  * Enumerables: Improve gas cost of removal in `EnumerableSet` and `EnumerableMap`.
  * Enumerables: Improve gas cost of lookup in `EnumerableSet` and `EnumerableMap`.
 
 ## 4.1.0 (2021-04-29)
 
- * `ERC20Votes`: add a new extension of the `ERC20` token with support for voting snapshots and delegation. This extension is compatible with Compound's `Comp` token interface. ([#2632](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2632))
-
-## Unreleased
-
  * `IERC20Metadata`: add a new extended interface that includes the optional `name()`, `symbol()` and `decimals()` functions. ([#2561](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2561))
  * `ERC777`: make reception acquirement optional in `_mint`. ([#2552](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2552))
  * `ERC20Permit`: add a `_useNonce` to enable further usage of ERC712 signatures. ([#2565](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2565))