fix: hide the card form's own title on the payment page

Mercado Pago's form titled both card options "Cartão de crédito ou débito";
the option above it already names the card.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/checkout.js

@@ -405,7 +405,10 @@
       customization:{paymentMethods:tipo==='debito'
           ? {maxInstallments:1,types:{excluded:['credit_card']}}
           : {maxInstallments:12,types:{excluded:['debit_card']}},
-        visual:{style:{customVariables:{baseColor:'#FFA81A',buttonTextColor:'#03060B'}}}},
+        // The option above already names the card; the form's own title
+        // ("crédito ou débito") would contradict it.
+        visual:{hideFormTitle:true,
+          style:{customVariables:{baseColor:'#FFA81A',buttonTextColor:'#03060B'}}}},
       callbacks:{
         onReady:()=>{},
         onError:error=>{ console.error(error); message('Erro no formulário do cartão. Confira os dados e tente de novo.'); },