Update BrowserSignin policy doc

Also mention that Android does not support =2 option in the policy
description.

Bug: 1022678
Change-Id: I29a36b8e86306e19e6ba834241ba429850acd449
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2125028Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Commit-Queue: Owen Min <zmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#754566}

components/policy/resources/policy_templates.json

@@ -12435,7 +12435,7 @@
 
       If the policy is set to "Enable browser sign-in," then the user is allowed to sign in to the browser and is automatically signed in to the browser when signed in to Google web services like Gmail. Being signed in to the browser means the user's account information will be kept by the browser. However, it does not mean that Chrome sync will be turned on per default; the user must separately opt-in to use this feature. Enabling this policy will prevent the user from turning off the setting that allows browser sign-in. To control the availability of Chrome sync, use the "SyncDisabled" policy.
 
-      If the policy is set to "Force browser sign-in" the user is presented with an account selection dialog and has to choose and sign in to an account to use the browser. This ensures that for managed accounts the policies associated with the account are applied and enforced. By default this turns on Chrome sync for the account, except for the case when sync was disabled by the domain admin or via the "SyncDisabled" policy. The default value of BrowserGuestModeEnabled will be set to false. Note that existing unsigned profiles will be locked and inaccessible after enabling this policy. For more information, see help center article: https://support.google.com/chrome/a/answer/7572556. This option does not support Linux and will fallback to "Enable browser sign-in" if used.
+      If the policy is set to "Force browser sign-in" the user is presented with an account selection dialog and has to choose and sign in to an account to use the browser. This ensures that for managed accounts the policies associated with the account are applied and enforced. By default this turns on Chrome sync for the account, except for the case when sync was disabled by the domain admin or via the "SyncDisabled" policy. The default value of BrowserGuestModeEnabled will be set to false. Note that existing unsigned profiles will be locked and inaccessible after enabling this policy. For more information, see help center article: https://support.google.com/chrome/a/answer/7572556. This option does not support Linux and Android, it will fallback to "Enable browser sign-in" if used.
 
       If this policy is not set then the user can decide if they want to enable the browser sign in option and use it as they see fit.''',
     },