Remove setHtml from buttons which don't need it

Using `->setHtml()` without HTML markup just for translation is useless
overkill. Setting caption directly with translation string is enough
Form has translator attached (with `$form->setTranslator($this->translator);`
and caption is automatically translated. See https://github.com/nette/forms/blob/4a70d32a3b40d096a4ae96410971dfde19e2456d/src/Forms/Controls/Button.php#L62

src/Forms/UserInvoiceFormFactory.php

@@ -108,8 +108,7 @@ public function create(ActiveRow $payment): Form
             ->getControlPrototype()
             ->setName('button')
             ->setAttribute('class', 'btn btn-success')
-            ->setAttribute('style', 'float: right')
-            ->setHtml($this->translator->translate('invoices.form.invoice.label.save'));
+            ->setAttribute('style', 'float: right');
 
         $defaults = [];