Fix debounce cancel

[aleclarson]

As mentioned in sodiray/radash#362, the cancel method should clear the timeout rather than cause the pending timeout to do nothing. The expected behavior is that calling the debounced function after cancelling it will result in an eventual invocation.

const fn = debounce({ delay: 100 }, () => console.log('hi'))

fn()
fn()
fn.cancel()
fn()
fn() // Logs "hi" once 100 ms after this call.

/cc @QTimort and @MarlonPassos-git as you both participated in sodiray/radash#362