[iOS] Disable configuration_policy for iOS builds.

Policy is no longer used on iOS, this is dead code cleanup.

BUG=550401

Review URL: https://codereview.chromium.org/1459223002

Cr-Original-Commit-Position: refs/heads/master@{#361313}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 3e5bdb1f6e6644eb6da1864e66ecc2eab790e479

common.gypi

@@ -864,6 +864,7 @@
         }],
 
         ['OS=="ios"', {
+          'configuration_policy%': 0,
           'disable_ftp_support%': 1,
           'enable_extensions%': 0,
           'enable_google_now%': 0,

config/features.gni

@@ -63,7 +63,6 @@ declare_args() {
   # proprietary codecs.
   proprietary_codecs = is_android || is_chrome_branded || is_chromecast
 
-  # TODO(GYP) This should be enabled on ios as well.
   enable_configuration_policy = !is_ios
 
   # Enables support for background apps.