cmd/internal/gc: remove dead code

Change-Id: Id5ce859bd4b6318dc9104f7377ae23d7f0bc30cd
Reviewed-on: https://go-review.googlesource.com/7640Reviewed-by: Minux Ma <minux@golang.org>

src/cmd/internal/gc/array.go

-// Copyright 2013 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 gc
-
-const (
-	DEFAULTCAPACITY = 16
-)