Minor, also update PHPMailerLite to use quoted-printable

Summary: See T5927.

Auditors: btrahan

src/applications/metamta/adapter/PhabricatorMailImplementationPHPMailerLiteAdapter.php

@@ -15,6 +15,7 @@ class PhabricatorMailImplementationPHPMailerLiteAdapter
     require_once $root.'/externals/phpmailer/class.phpmailer-lite.php';
     $this->mailer = new PHPMailerLite($use_exceptions = true);
     $this->mailer->CharSet = 'utf-8';
+    $this->mailer->Encoding = 'quoted-printable';
 
     // By default, PHPMailerLite sends one mail per recipient. We handle
     // multiplexing higher in the stack, so tell it to send mail exactly