mac: Remove edit_xibs.sh.

chrome_nibs.gyp went away a while ago, and gyp is no longer deps'd in.

Bug: none
Change-Id: I71d7503b0f95ff15575653da7efe35e4e62a6fcd
Reviewed-on: https://chromium-review.googlesource.com/c/1371928Reviewed-by: Robert Sesek <rsesek@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615542}

build/mac/edit_xibs.sh

-#!/bin/sh
-
-# Copyright (c) 2012 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-# This script is a convenience to run GYP for /src/chrome/chrome_nibs.gyp
-# with the Xcode generator (as you likely use ninja). Documentation:
-#   http://dev.chromium.org/developers/design-documents/mac-xib-files
-
-set -e
-
-RELSRC=$(dirname "$0")/../..
-SRC=$(cd "$RELSRC" && pwd)
-export PYTHONPATH="$PYTHONPATH:$SRC/build"
-export GYP_GENERATORS=xcode
-"$SRC/tools/gyp/gyp" -I"$SRC/build/common.gypi" "$SRC/chrome/chrome_nibs.gyp"
-echo "You can now edit XIB files in Xcode using:"
-echo "  $SRC/chrome/chrome_nibs.xcodeproj"