Remove future flag from Kerberos policies

Remove deprecated future tag from Kerberos policies. Also, update
supported_on tag to version 87, which was on the stable channel when
the feature was publicly launched (on the server side). Also, M87
already has all the fixes we added during the TT phase.

BYPASS_POLICY_COMPATIBILITY_CHECK=These are launched policies with
future tag.

Bug: b:131255983
Change-Id: I9b99cbc540203fcc68997d6ef938b54746b7bbf5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2616706Reviewed-by: Owen Min <zmin@chromium.org>
Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Commit-Queue: Maksim Ivanov <emaxx@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842047}

components/policy/resources/policy_templates.json

@@ -20987,13 +20987,12 @@
       'owners': ['file://chrome/browser/chromeos/kerberos/OWNERS'],
       'type': 'main',
       'schema': { 'type': 'boolean' },
-      'supported_on': ['chrome_os:75-'],
+      'supported_on': ['chrome_os:87-'],
       'supported_chrome_os_management': ['google_cloud'],
       'features': {
         'dynamic_refresh': True,
         'per_profile': False,
       },
-      'future': True,
       'example_value': True,
       'id': 557,
       'caption': '''Enable Kerberos functionality''',
@@ -21009,13 +21008,12 @@
       'owners': ['file://chrome/browser/chromeos/kerberos/OWNERS'],
       'type': 'main',
       'schema': { 'type': 'boolean' },
-      'supported_on': ['chrome_os:75-'],
+      'supported_on': ['chrome_os:87-'],
       'supported_chrome_os_management': ['google_cloud'],
       'features': {
         'dynamic_refresh': True,
         'per_profile': False,
       },
-      'future': True,
       'example_value': True,
       'id': 558,
       'caption': '''Enable 'Remember password' feature''',
@@ -21031,13 +21029,12 @@
       'owners': ['file://chrome/browser/chromeos/kerberos/OWNERS'],
       'type': 'main',
       'schema': { 'type': 'boolean' },
-      'supported_on': ['chrome_os:75-'],
+      'supported_on': ['chrome_os:87-'],
       'supported_chrome_os_management': ['google_cloud'],
       'features': {
         'dynamic_refresh': True,
         'per_profile': False,
       },
-      'future': True,
       'example_value': True,
       'id': 559,
       'caption': '''Users can add Kerberos accounts''',
@@ -21082,13 +21079,12 @@
           'required': ['principal'],
         },
       },
-      'supported_on': ['chrome_os:75-'],
+      'supported_on': ['chrome_os:87-'],
       'supported_chrome_os_management': ['google_cloud'],
       'features': {
         'dynamic_refresh': True,
         'per_profile': False,
       },
-      'future': True,
       'example_value': [
         {
           "principal":"${LOGIN_EMAIL}",