Remove metamta.differential.unified-comment-context and explain it in ExtraConfigSetupCheck

Summary: Ref T10694. This setting no longer has any effect: we always show a limited amount of context now.

Test Plan: `grep`

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10694

Differential Revision: https://secure.phabricator.com/D15886

src/applications/config/check/PhabricatorExtraConfigSetupCheck.php

@@ -310,6 +310,10 @@ final class PhabricatorExtraConfigSetupCheck extends PhabricatorSetupCheck {
       'notification.enabled' => $aphlict_reason,
       'notification.client-uri' => $aphlict_reason,
       'notification.server-uri' => $aphlict_reason,
+
+      'metamta.differential.unified-comment-context' => pht(
+        'Inline comments are now always rendered with a limited amount '.
+        'of context.'),
     );
 
     return $ancient_config;

src/applications/differential/config/PhabricatorDifferentialConfigOptions.php

@@ -287,21 +287,6 @@ final class PhabricatorDifferentialConfigOptions
         'unified')
         ->setDescription(
           pht("Format for inlined or attached patches: 'git' or 'unified'.")),
-      $this->newOption(
-        'metamta.differential.unified-comment-context',
-        'bool',
-        false)
-        ->setBoolOptions(
-          array(
-            pht('Show context'),
-            pht('Do not show context'),
-          ))
-        ->setSummary(pht('Show diff context around inline comments in email.'))
-        ->setDescription(
-          pht(
-            'Normally, inline comments in emails are shown with a file and '.
-            'line but without any diff context. Enabling this option adds '.
-            'diff context and the comment thread.')),
     );
   }