Removing duplicate check

This should be done inside the function in case someone to call the
method directly.

The check is also already done for add_options_page.

Related to ActiveCampaign#12

postmark.php

@@ -24,10 +24,6 @@ function __construct() {
 
 
     function init() {
-        if ( ! current_user_can( 'manage_options' ) ) {
-            return;
-        }
-
         add_action( 'admin_menu', array( $this, 'admin_menu' ) );
         add_action( 'wp_ajax_postmark_save', array( $this, 'save_settings' ) );
         add_action( 'wp_ajax_postmark_test', array( $this, 'send_test_email' ) );