Use built-in clear function to reset xorset

[Juneezee]

Reference: https://go.dev/ref/spec#Clear

The built-in clear function introduced in Go 1.21 does the job of resetSets function.

Playground example: https://go.dev/play/p/7d4DsuYqY2t

package main

import "fmt"

type xorset struct {
	xormask uint64
	count   uint32
}

func main() {
	sets0 := []xorset{
		xorset{1, 1},
		xorset{2, 2},
		xorset{3, 3},
	}

	fmt.Println(sets0)
	clear(sets0)
	fmt.Println(sets0)
}

[{1 1} {2 2} {3 3}]
[{0 0} {0 0} {0 0}]

[lemire]

Sounds reasonable.