Add changelog entry for 3.4.1

CHANGELOG.md

@@ -95,6 +95,10 @@ Make sure you're using git or another version control system to be able to recov
 
 Some further changes have been done between the different beta iterations. Transitions made during this period are configured in the `migrate-imports` script. Consequently, you can upgrade from any previous 4.0-beta.x version using the same script as described in the *How to upgrade from 3.x* section.
 
+## 3.4.1 (2021-03-03)
+
+ * `ERC721`: made `_approve` an internal function (was private).
+
 ## 3.4.0 (2021-02-02)
 
  * `BeaconProxy`: added new kind of proxy that allows simultaneous atomic upgrades. ([#2411](/~https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2411))