reflect: add missing copyright header

Change-Id: I5a2f7203f83be02b03aa7be5fe386e485bf68ca3
Reviewed-on: https://go-review.googlesource.com/c/go/+/336189
Reviewed-by: Ian Lance Taylor <[email protected]>
Trust: Robert Findley <[email protected]>

Author: wdvxdr1123

src/reflect/visiblefields.go

@@ -1,3 +1,7 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
 package reflect
 
 // VisibleFields returns all the visible fields in t, which must be a

src/reflect/visiblefields_test.go

@@ -1,3 +1,7 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
 package reflect_test
 
 import (