Revert "Add checkout_nacl gclient flag (default true) (attempt #2)"

This reverts commit 53c4c334b38e95ec2fea2498354ba4864cb54585
(https://chromium-review.googlesource.com/c/702434/).

TBR=dpranke,dschuff

Bug: 773185, 756688
Change-Id: Id66e32b07b05957b4a1265da723b14fb92123d7f
Reviewed-on: https://chromium-review.googlesource.com/713374
Reviewed-by: Paweł Hajdan Jr. <phajdan.jr@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#507998}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: da2f3313e4c8e4de9c1011d3ed3e80a1bea5e04c

.gitignore

@@ -2,7 +2,6 @@
 # mirror in DEPS. Without it, a lot is wiped and re-downloaded for each sync.
 /android/bin
 /android/binary_size/apks/**/*.apk
-/config/gclient_args.gni
 /Debug
 /Debug_x64
 /goma