all: use Go 1.22 range-over-int

Updates #11058

Change-Id: I35e7ef9b90e83cac04ca93fd964ad00ed5b48430
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

tstest/clock_test.go

@@ -153,7 +153,7 @@ func TestZeroInitClock(t *testing.T) {
 		t.Errorf("clock has step %v, want 0", step)
 	}
 
-	for i := 0; i < 10; i++ {
+	for i := range 10 {
 		if got := clock.Now(); !got.Equal(start) {
 			t.Errorf("step %v: clock.Now() = %v, want %v", i, got, start)
 		}