Bump mac deployment target to 10.9

BUG=webrtc:6431

Review-Url: https://codereview.webrtc.org/2488943002
Cr-Commit-Position: refs/heads/master@{#15004}
diff --git a/webrtc/sdk/BUILD.gn b/webrtc/sdk/BUILD.gn
index d54961c..53602a4 100644
--- a/webrtc/sdk/BUILD.gn
+++ b/webrtc/sdk/BUILD.gn
@@ -16,14 +16,14 @@
 }
 
 group("sdk") {
-  if (is_ios || (is_mac && mac_deployment_target == "10.7")) {
+  if (is_ios || is_mac) {
     public_deps = [
       ":rtc_sdk_framework_objc",
     ]
   }
 }
 
-if (is_ios || (is_mac && mac_deployment_target == "10.7")) {
+if (is_ios || is_mac) {
   config("rtc_sdk_common_objc_config") {
     include_dirs = [
       "objc/Framework/Classes",