Remove build_override for macOS min SDK and deployment target.

v8 now uses the same SDK as Chromium, even when built as a standalone project.
The deployment target override has no effect.

Bug: chromium:740693
Change-Id: I089f74d5ad1590ff7167564f83b0110620a92ef9
Reviewed-on: https://chromium-review.googlesource.com/565887Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46686}

build_overrides/build.gni

@@ -2,9 +2,6 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-mac_sdk_min_build_override = "10.10"
-mac_deployment_target_build_override = "10.7"
-
 # Variable that can be used to support multiple build scenarios, like having
 # Chromium specific targets in a client project's GN file etc.
 build_with_chromium = false