Reformat Module\Settings\UserExport

- Import IHandleUserSessions and DbaDefinition object in constructor
- Convert remaining double quotes to single quotes
- Convert static methods to dynamic to use class properties
- Remove unused POST permission from route

static/routes.config.php

@@ -574,7 +574,7 @@ return [
 			'/photo[/new]'         => [Module\Settings\Profile\Photo\Index::class, [R::GET, R::POST]],
 			'/photo/crop/{guid}'   => [Module\Settings\Profile\Photo\Crop::class,  [R::GET, R::POST]],
 		],
-		'/userexport[/{action}]' => [Module\Settings\UserExport::class,             [R::GET, R::POST]],
+		'/userexport[/{action}]' => [Module\Settings\UserExport::class,            [R::GET         ]],
 	],
 
 	'/network' => [