Make ERC4626 _deposit and _withdraw internal virtual (#3504)

(cherry picked from commit 74738721dc9cfa820687f6b700d2583b16a21c0d)

contracts/token/ERC20/extensions/ERC4626.sol

@@ -176,7 +176,7 @@ abstract contract ERC4626 is ERC20, IERC4626 {
         address receiver,
         uint256 assets,
         uint256 shares
-    ) private {
+    ) internal virtual {
         // If _asset is ERC777, `transferFrom` can trigger a reenterancy BEFORE the transfer happens through the
         // `tokensToSend` hook. On the other hand, the `tokenReceived` hook, that is triggered after the transfer,
         // calls the vault, which is assumed not malicious.
@@ -199,7 +199,7 @@ abstract contract ERC4626 is ERC20, IERC4626 {
         address owner,
         uint256 assets,
         uint256 shares
-    ) private {
+    ) internal virtual {
         if (caller != owner) {
             _spendAllowance(owner, caller, shares);
         }