Remove "metamta.precedence-bulk" option (always enable it)

Summary: Ref T7746. This might possibly improve deliverability. Or might make it worse. Who knows?

Test Plan: `grep`

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7746

Differential Revision: https://secure.phabricator.com/D12266

src/applications/config/check/PhabricatorExtraConfigSetupCheck.php

@@ -241,6 +241,10 @@ final class PhabricatorExtraConfigSetupCheck extends PhabricatorSetupCheck {
       'metamta.differential.reply-handler' => $reply_handler_reason,
       'metamta.maniphest.reply-handler' => $reply_handler_reason,
       'metamta.package.reply-handler' => $reply_handler_reason,
+
+      'metamta.precedence-bulk' => pht(
+        'Phabricator now always sends transaction mail with '.
+        '"Precedence: bulk" to improve deliverability.'),
     );
 
     return $ancient_config;

src/applications/config/option/PhabricatorMetaMTAConfigOptions.php

@@ -271,14 +271,6 @@ EODOC
           ))
         ->setSummary(pht('Show email preferences link in email.'))
         ->setDescription($email_preferences_description),
-      $this->newOption('metamta.precedence-bulk', 'bool', false)
-        ->setBoolOptions(
-          array(
-            pht('Add "Precedence: bulk" Header'),
-            pht('No "Precedence: bulk" Header'),
-          ))
-        ->setSummary(pht('Control the "Precedence: bulk" header.'))
-        ->setDescription($bulk_description),
       $this->newOption('metamta.re-prefix', 'bool', false)
         ->setBoolOptions(
           array(

src/applications/metamta/storage/PhabricatorMetaMTAMail.php

@@ -545,10 +545,8 @@ final class PhabricatorMetaMTAMail extends PhabricatorMetaMTADAO {
             break;
           case 'is-bulk':
             if ($value) {
-              if (PhabricatorEnv::getEnvConfig('metamta.precedence-bulk')) {
               $mailer->addHeader('Precedence', 'bulk');
             }
-            }
             break;
           case 'thread-id':