[TASK] Remove legacy support for Tx_ prefixed class style

This class naming style has not been supported since 7.6 LTS compatible versions were released. Vendor-less controller classes are still supported; another patch may remove this support (and mark vendor usage as the only supported usage across the extension).

Classes/Helper/Resolver.php

@@ -148,10 +148,6 @@ private static function buildControllerClassNameFromExtensionKeyAndControllerTyp
         } else {
             $extensionName = ExtensionNamingUtility::getExtensionName($extensionKey);
             $potentialClassName = $extensionName . '\\Controller\\' . $controllerName . 'Controller';
-            // @TODO remove legacy
-            if (false === class_exists($potentialClassName)) {
-                $potentialClassName = 'Tx_' . $extensionName . '_Controller_' . $controllerName . 'Controller';
-            }
         }
         return $potentialClassName;
     }