Update CHANGELOG.md

Author: nventuro

CHANGELOG.md

@@ -5,6 +5,9 @@
 ### New features
  * `SafeCast.toUintXX`: new library for integer downcasting, which allows for safe operation on smaller types (e.g. `uint32`) when combined with `SafeMath`. ([#1926](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1926))
 
+### Improvements
+ * `ERC777`: `_burn` is now internal, providing more flexibility and making it easier to create tokens that deflate. ([#1908]https://github.com/OpenZeppelin/openzeppelin-contracts/pull/1908))
+
 ### Breaking changes
  * `ERC165Checker` now requires a minimum Solidity compiler version of 0.5.10. ([#1829](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1829))