[v4] clear warning about `sync` 

after this is merged: https://github.com/pancakeswap/pancake-v4-core/pull/165

if a user does this:
- vault.sync(token1)
- transfer token1 to vault
- forget to call vault.settle(token1) but call vault.sync(token2)

then whatever token sent to vault might be lost if transaction didn't revert 