update rules

Author: prolic

src/Prooph.php

@@ -93,7 +93,7 @@ public function getRules(): array
             'return_type_declaration' => true,
             'semicolon_after_instruction' => true,
             'short_scalar_cast' => true,
-            'simplified_null_return' => true,
+            'simplified_null_return' => false,
             'single_blank_line_at_eof' => true,
             'single_class_element_per_statement' => true,
             'single_import_per_statement' => true,