Remove NetPrefObserver class and two prefs that do not do anything.

components/policy/resources/policy_templates.json

 {
 # policy_templates.json - Metafile for policy templates
 #
 # The content of this file is evaluated as a Python expression.
 #
 # This file is used as input to generate the following policy templates:
 # ADM, ADMX+ADML, MCX/plist and html documentation.
 #
 # Policy templates are user interface definitions or documents about the
 # policies that can be used to configure Chrome. Each policy is a name-value
@@ skipping 368 matching lines @@
       If you disable this setting, search suggestions are never used.
 
       If you enable or disable this setting, users cannot change or override this setting in <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph>.
 
       If this policy is left not set, this will be enabled but the user will be able to change it.''',
     },
     {
       'name': 'DnsPrefetchingEnabled',
       'type': 'main',
       'schema': { 'type': 'boolean' },
-      'supported_on': ['chrome.*:8-', 'chrome_os:11-', 'android:30-'],
+      'supported_on': ['chrome.*:8-53', 'chrome_os:11-53', 'android:30-53'],
       'features': {
         'can_be_recommended': True,
         'dynamic_refresh': True,
         'per_profile': True,
       },
+      'deprecated': True,
       'example_value': True,
       'id': 7,
       'caption': '''Enable network prediction''',
       'tags': [],
-      'desc': '''Enables network prediction in <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph> and prevents users from changing this setting.
+      'desc': '''This policy is deprecated in M48 in favor of NetworkPredictionOptions, and removed in M54.
+
+      Enables network prediction in <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph> and prevents users from changing this setting.
 
       This controls not only DNS prefetching but also TCP and SSL preconnection and prerendering of web pages. The policy name refers to DNS prefetching for historical reasons.
 
       If you enable or disable this setting, users cannot change or override this setting in <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph>.
 
       If this policy is left not set, this will be enabled but the user will be able to change it.''',
     },
     {
       'name': 'NetworkPredictionOptions',
       'type': 'int-enum',
@@ skipping 53 matching lines @@
       'desc': '''Allows to turn off WPAD (Web Proxy Auto-Discovery) optimization in <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph>.
 
       If this policy is set to false, WPAD optimization is disabled causing <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph> to wait longer for DNS-based WPAD servers.  If the policy is not set or is enabled, WPAD optimization is enabled.
 
       Independent of whether or how this policy is set, the WPAD optimization setting cannot be changed by users.''',
     },
     {
       'name': 'DisableSpdy',
       'type': 'main',
       'schema': { 'type': 'boolean' },
-      'supported_on': ['chrome.*:8-', 'chrome_os:11-', 'android:30-'],
+      'supported_on': ['chrome.*:8-53', 'chrome_os:11-53', 'android:30-53'],
       'features': {
         'dynamic_refresh': True,
         'per_profile': False,
       },
       'deprecated': True,
       'example_value': True,
       'id': 8,
       'caption': '''Disable SPDY protocol''',
       'tags': [],
-      'desc': '''This policy is deprecated, because SPDY/3.1 support is removed.
+      'desc': '''This policy is deprecated in M53 and removed in M54, because SPDY/3.1 support is removed.
 
       Disables use of the SPDY protocol in <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph>.
 
       If this policy is enabled the SPDY protocol will not be available in <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph>.
 
       Setting this policy to disabled will allow the usage of SPDY.
 
       If this policy is left not set, SPDY will be available.''',
     },
     {
@@ skipping 8374 matching lines @@
       'desc': '''Text appended in parentheses next to the policies top-level container to indicate that those policies are of the Recommended level''',
       'text': 'Default Settings (users can override)',
     },
     'doc_complex_policies_on_windows': {
       'desc': '''Text pointing the user to a help article for complex policies on Windows''',
       'text': '''encoded as a JSON string, for details see <ph name="COMPLEX_POLICIES_URL">https://www.chromium.org/administrators/complex-policies-on-windows<ex>https://www.chromium.org/administrators/complex-policies-on-windows</ex></ph>''',
     },
   },
   'placeholders': [],
 }