all: Remove usage of deprecated io/ioutil (#7971)

As of Go 1.16 io/ioutil is deprecated. This replaces usage with the
corresponding functions in package os and package io.

lib/weakhash/weakhash_test.go

@@ -13,7 +13,6 @@ import (
 	"bytes"
 	"context"
 	"io"
-	"io/ioutil"
 	"os"
 	"reflect"
 	"testing"
@@ -22,7 +21,7 @@ import (
 var payload = []byte("abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz")
 
 func TestFinder(t *testing.T) {
-	f, err := ioutil.TempFile("", "")
+	f, err := os.CreateTemp("", "")
 	if err != nil {
 		t.Error(err)
 	}