Remove android build dir nesting restriction

It appears that android builds no longer have to be nested exactly two
levels under //. A build with one level works, so the assert in gn is
no longer helpful.

BUG=412935
R=agrieve@chromium.org

Review-Url: https://codereview.chromium.org/2544493002
Cr-Original-Commit-Position: refs/heads/master@{#435410}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 77a846f5c24714f5cde96d6e3fd124d501206799

config/android/config.gni

@@ -5,10 +5,6 @@
 # This file contains common system config stuff for the Android build.
 
 if (is_android) {
-  assert(rebase_path("//", root_build_dir) == "../../",
-         "Android output directory must be nested 2 levels within src/ (" +
-             "e.g.: out-gn/Debug). http://crbug.com/412935")
-
   import("//build_overrides/build.gni")
 
   has_chrome_android_internal =