Android: Remove now-unused incremental_apk_by_default

Bug: 1013688
Change-Id: I3896525dd57b8590a0f6aad184f9e5a8bc7133c1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1879662
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Eric Stevenson <estevenson@chromium.org>
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Eric Stevenson <estevenson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709592}

build/config/android/config.gni

@@ -216,9 +216,6 @@ if (is_android || is_chromeos) {
     trichrome_shared_assets = android_sdk_release == "q"
   }
 
-  # TODO(agrieve): Remove once unused downstream.
-  incremental_apk_by_default = incremental_install
-
   if (notouch_build && defined(extra_keymappings)) {
     keycode_conversion_data_android_path = extra_keymappings
   }