Remove unused build override

build_overrides/build.gni

 # Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
-# See https://bugs.chromium.org/p/webrtc/issues/detail?id=5453.
-# Some WebRTC targets require the 10.7 deployment version of the Mac SDK and a
-# 10.11 min SDK but those targets are only used in non-Chromium builds. We can
-# remove this when Chromium drops 10.6 support and also requires 10.7.
+# Some WebRTC targets require a 10.11 min SDK but those targets are only
+# used in non-Chromium builds.
 mac_sdk_min_build_override = "10.11"
-mac_deployment_target_build_override = "10.9"
 
 # Some non-Chromium builds don't support building java targets.
 enable_java_templates = true
 
 # Some non-Chromium builds don't use Chromium's third_party/binutils.
 linux_use_bundled_binutils_override = true
 
 # 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
 
 # Use our own suppressions files.
 asan_suppressions_file = "//build/sanitizers/asan_suppressions.cc"
 lsan_suppressions_file = "//webrtc/build/sanitizers/lsan_suppressions_webrtc.cc"
 tsan_suppressions_file = "//webrtc/build/sanitizers/tsan_suppressions_webrtc.cc"
 
 # Android lint suppressions file
 lint_suppressions_file = "//webrtc/build/android/suppressions.xml"
 
 # For Chromium, Android 32-bit non-component, non-clang builds hit a 4GiB size
 # limit, making them requiring symbol_level=2. WebRTC doesn't hit that problem
 # so we just ignore that assert. See https://crbug.com/648948 for more info.
 ignore_elf32_limitations = true
 
 # Use system Xcode installation instead of the Chromium bundled Mac toolchain,
 # since it contains only SDK 10.11, not 10.12 which WebRTC needs.
 use_system_xcode = true
 
 android_test_runner_script = "../../webrtc/build/android/test_runner.py"