Letting go of expectation towards the fruit of actions, is about performing all actions without attachment towards the actions and the fruit of actions, but allowing the fruit of actions to be what it is. This is different from the idea of “After I performed some (good or bad) actions, I do not want to receive anything (good or bad) in return”, or “I do not expect something in return that is beyond my expectation.”
As all actions will definitely bring some pleasant or unpleasant consequences in return, whether we want to receive something in return or not, whether we have attachment and expectation towards the fruit of actions or not, or whether the fruit of actions is the way that we think it should be or not. The fruit of actions will be there as it is. It won’t become more or less, nor disappear.