Use plural name

Nyholm · Nyholm · commit 33c7b127ac63 · 2021-04-19T21:56:41.000+02:00
diff --git a/forms.rst b/forms.rst
@@ -348,7 +348,7 @@ can set this option to generate forms compatible with the Bootstrap 4 CSS framew
         use Symfony\Config\TwigConfig;
 
         return static function (TwigConfig $twig) {
-            $twig->formTheme(['bootstrap_4_layout.html.twig']);
+            $twig->formThemes(['bootstrap_4_layout.html.twig']);
 
             // ...
         };
