Remove nullability from $tmpDir property

The @var annotation for the $tmpDir property has been updated to `non-empty-string` to remove the possibility of it being null. This change ensures that the temporary directory for generated proxy classes must always be a non-empty string.

src/Aspect.php

@@ -42,7 +42,7 @@ final class Aspect
     /**
      * Temporary directory for generated proxy classes
      *
-     * @var non-empty-string|null
+     * @var non-empty-string
      */
     private $tmpDir;