Enable Clank authenticator for default and Canary builds.

This shouldn't break the release builder because the native code will
still be constant across release modes.

BUG=1002262

Change-Id: I86db7fd5cc23c791012ac68afad2806ef35d44bc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2135872
Commit-Queue: Martin Kreichgauer <martinkr@google.com>
Auto-Submit: Adam Langley <agl@chromium.org>
Reviewed-by: Martin Kreichgauer <martinkr@google.com>
Cr-Commit-Position: refs/heads/master@{#756344}

chrome/android/features/cablev2_authenticator/config.gni

@@ -5,5 +5,6 @@
 import("//build/config/android/channel.gni")
 
 declare_args() {
-  enable_android_cablev2_authenticator = false
+  enable_android_cablev2_authenticator =
+      android_channel == "default" || android_channel == "canary"
 }