[CRD iOS] Remove the supports_app_initializer flag

Follow up CL for adding AppInitializer.

Bug: 746105
Change-Id: I45fd6e39cfd3d748e185bc1e515f5be9ee33cc48
Reviewed-on: https://chromium-review.googlesource.com/578708Reviewed-by: Scott Nichols <nicholss@chromium.org>
Commit-Queue: Yuwei Huang <yuweih@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488742}

remoting/ios/app/remoting_ios_tmpl.gni

@@ -9,11 +9,6 @@ import("//build/util/process_version.gni")
 import("//remoting/build/config/remoting_build.gni")
 import("//remoting/credits/credits.gni")
 
-# TODO(yuweih): Temporary flag. Remove once it rolls into downstream.
-declare_args() {
-  supports_app_initializer = true
-}
-
 _remoting_ios_app_source_dir = get_path_info("./", "abspath")
 
 # Arguments