Fix method visibility for PhabricatorApplication methods

Summary: Ref T6822.

Test Plan: Visual inspection. These methods are only called from within the `PhabricatorApplication` class.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T6822

Differential Revision: https://secure.phabricator.com/D11243

src/applications/countdown/application/PhabricatorCountdownApplication.php

@@ -48,7 +48,7 @@ final class PhabricatorCountdownApplication extends PhabricatorApplication {
     );
   }
 
-  public function getCustomCapabilities() {
+  protected function getCustomCapabilities() {
     return array(
       PhabricatorCountdownDefaultViewCapability::CAPABILITY => array(
         'caption' => pht('Default view policy for new countdowns.'),

src/applications/harbormaster/application/PhabricatorHarbormasterApplication.php

@@ -81,7 +81,7 @@ final class PhabricatorHarbormasterApplication extends PhabricatorApplication {
     );
   }
 
-  public function getCustomCapabilities() {
+  protected function getCustomCapabilities() {
     return array(
       HarbormasterManagePlansCapability::CAPABILITY => array(
         'caption' => pht('Can create and manage build plans.'),

src/applications/slowvote/application/PhabricatorSlowvoteApplication.php

@@ -55,7 +55,7 @@ final class PhabricatorSlowvoteApplication extends PhabricatorApplication {
     );
   }
 
-  public function getCustomCapabilities() {
+  protected function getCustomCapabilities() {
     return array(
       PhabricatorSlowvoteDefaultViewCapability::CAPABILITY => array(
         'caption' => pht('Default view policy for new polls.'),