fix: OCI8 Forge always sets NOT NULL when BOOLEAN is specified

Author: kenjis

system/Database/OCI8/Forge.php

@@ -254,7 +254,6 @@ protected function _attributeType(array &$attributes)
                 $attributes['TYPE']       = 'NUMBER';
                 $attributes['CONSTRAINT'] = 1;
                 $attributes['UNSIGNED']   = true;
-                $attributes['NULL']       = false;
 
                 return;