Update SecondaryGoogleAccountSigninAllowed policy's documentation

With Chrome OS Account Manager enabled,
SecondaryGoogleAccountSigninAllowed applies to the unified account list
in Chrome OS Account Manager, and not just Chrome content area, as the
policy documentation claims.

Update the documentation to reflect this fact.

Another related policy: AllowedDomainsForApps does not require any
change.

Bug: 967206
Change-Id: Ifde3d6c8a68fb2ec22006bb4cdcc1b0707f15351
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1768464Reviewed-by: Bartosz Fabianowski <bartfab@chromium.org>
Commit-Queue: Kush Sinha <sinhak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#690333}

components/policy/resources/policy_templates.json

@@ -5886,19 +5886,19 @@
       'schema': { 'type': 'boolean' },
       'supported_on': ['chrome_os:65-'],
       'features': {
-        # The case where a user is already signed into an unmanaged account from the content area cannot be handled right now and hence this is not dynamic.
+        # The case where a user is already signed into an unmanaged account cannot be handled right now and hence this is not dynamic.
         'dynamic_refresh': False,
         'per_profile': True,
       },
       'example_value': False,
       'id': 406,
-      'caption': '''Allow Multiple Sign-in Within the Browser''',
+      'caption': '''Allow Sign-in To Additional Google Accounts''',
       'tags': [],
-      'desc': '''This setting allows users to switch between Google accounts within the content area of their browser window after they sign into their <ph name="PRODUCT_OS_NAME">$2<ex>Google Chrome OS</ex></ph> device.
+      'desc': '''This setting allows users to switch between Google Accounts within the content area of their browser window and in Android applications, after they sign into their <ph name="PRODUCT_OS_NAME">$2<ex>Google Chrome OS</ex></ph> device.
 
-      If this policy is set to false, signing in to a different account from non-Incognito browser content area will not be allowed.
+      If this policy is set to false, signing in to a different Google Account from a non-Incognito browser content area and Android applications will not be allowed.
 
-      If this policy is unset or set to true, the default behavior will be used: signing in to a different account from the browser content area will be allowed, except for child accounts where it will be blocked for non-Incognito content area.
+      If this policy is unset or set to true, the default behavior will be used: signing in to a different Google Account from the browser content area and Android applications will be allowed, except for child accounts where it will be blocked for non-Incognito content area.
 
       In case signing in to a different account shouldn't be allowed via the Incognito mode, consider blocking that mode using the IncognitoModeAvailability policy.