FIX Remove mapping for CMS 5.1 to elemental userforms (#122)

While this mapping is technically correct, it's resulting in php linting
failing, because installer 5.1 is installed which was before generic
typing was added to the lists.

Author: GuySartorelli

consts.php

@@ -357,7 +357,6 @@
         'silverstripe-elemental' => '5.1',
         'silverstripe-elemental-bannerblock' => '3.1',
         'silverstripe-elemental-fileblock' => '3.1',
-        'silverstripe-elemental-userforms' => '4.1',
         'silverstripe-environmentcheck' => '3.0',
         'silverstripe-externallinks' => '3.1',
         'silverstripe-fluent' => '7.0',