Make policy description public

Bug: 676195
Change-Id: I75ba73a7ee75d446c8d5b79d8f4c45aed569940d
Reviewed-on: https://chromium-review.googlesource.com/1201855Reviewed-by: Sergey Poromov <poromov@chromium.org>
Commit-Queue: Denis Kuznetsov <antrim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#588388}

components/policy/resources/policy_templates.json

@@ -11827,16 +11827,15 @@
       'name': 'DeviceHostnameTemplate',
       'type': 'string',
       'schema': { 'type': 'string' },
-      'supported_on': ['chrome_os:64-'],
+      'supported_on': ['chrome_os:65-'],
       'device_only': True,
-      'future': True,
       'features': {
         'dynamic_refresh': True,
         'per_profile': False,
       },
       'example_value': 'chromebook-${ASSET_ID}',
       'id': 403,
-      'caption': '''Device network hostname''',
+      'caption': '''Device network hostname template''',
       'tags': [],
       'desc': '''Determine the hostname of the device used in DHCP requests.