Android: Fix gn gen failure for official builds when check_android_configuration is not set

Was hitting this locally:
2019-10-22 04:06:38 -0400 ERROR at //chrome/android/BUILD.gn:2339:11: Assignment had no effect.
2019-10-22 04:06:38 -0400           "monochrome_public_bundle.android_manifest.failed"
2019-10-22 04:06:38 -0400           ^-------------------------------------------------

Bug: 1011227
Change-Id: I850fc129d8c2e1c7190266735f2fab97f7efebc8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1873240
Commit-Queue: Mohamed Heikal <mheikal@chromium.org>
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Mohamed Heikal <mheikal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#708221}

chrome/android/BUILD.gn

@@ -2383,7 +2383,8 @@ if (public_android_sdk) {
     # Having //clank present causes different flags because of how play services
     # is wired up.
     # The channel is required because manifest entries vary based on channel.
-    if (!enable_chrome_android_internal && android_channel == "stable") {
+    if (check_android_configuration && !enable_chrome_android_internal &&
+        android_channel == "stable") {
       verify_android_configuration = true
     }
   }