time: time/internal_test.go remove redundant type conversion

Change-Id: I5aaea4918f024a87146ba54a8d5307658d722fe9
Reviewed-on: https://go-review.googlesource.com/c/go/+/589635
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: hui zhou <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>

Author: hxzhouh

Diff for: src/time/internal_test.go

@@ -47,7 +47,7 @@ func CheckRuntimeTimerPeriodOverflow() {
 	// We manually create a runtimeTimer with huge period, but that expires
 	// immediately. The public Timer interface would require waiting for
 	// the entire period before the first update.
-	t := (*Timer)(newTimer(runtimeNano(), 1<<63-1, empty, nil, nil))
+	t := newTimer(runtimeNano(), 1<<63-1, empty, nil, nil)
 	defer t.Stop()
 
 	// If this test fails, we will either throw (when siftdownTimer detects