add comment for Approval change

Author: d10r

packages/ethereum-contracts/CHANGELOG.md

@@ -16,6 +16,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - bump solc to "0.8.30".
 - Changed EVM target from `paris` to `shanghai` because now all networks with supported Superfluid deployment support it.
 - Emit ERC20 `Transfer` events (with amount 0) on CFA and GDA actions potentially leading to account balance changes. This shall help indexers to keep track of SuperToken holders and account balances.
+- Don't emit ERC20 `Approval` events on `transferFrom` operations. This is consistent with the OpenZeppelin ERC20 implementation from v5 onwards. Change effective only for SuperTokens using the latest logic.
 
 ### Fixed
 - `ISuperfluidPool`: `getClaimable` and `getClaimableNow` could previously return non-zero values for connected pools, which was inconsistent with what `claimAll` would actually do in this situation (claim nothing).

packages/ethereum-contracts/contracts/superfluid/SuperToken.sol

@@ -513,6 +513,10 @@ contract SuperToken is
      *
      * By default (when calling {_approve}) the flag is set to true. On the other hand, approval changes made
      * during the `transferFrom` operation set the flag to false.
+     *
+     * Note: In the OpenZeppelin implementation, from v5 onwards, {transferFrom} doesn't emit an {Approval} event.
+     * By adding this overloaded function and using it for {transferFrom}, we replicate that change,
+     * because it seems semantically more correct.
      */
     function _approve(address account, address spender, uint256 amount, bool emitEvent)
         internal