yuzu/applets/software_keyboard: Use QDialogButtonBox standard buttons instead of custom buttons

Like the previous change, this allows Qt to handle proper translations
of the UI buttons, rather than us needing to handle it.

src/yuzu/applets/software_keyboard.cpp

@@ -75,13 +75,13 @@ QtSoftwareKeyboardDialog::QtSoftwareKeyboardDialog(
         length_label->setText(QStringLiteral("%1/%2").arg(text.size()).arg(parameters.max_length));
     });
 
-    buttons = new QDialogButtonBox;
-    buttons->addButton(tr("Cancel"), QDialogButtonBox::RejectRole);
-    buttons->addButton(parameters.submit_text.empty()
-                           ? tr("OK")
-                           : QString::fromStdU16String(parameters.submit_text),
-                       QDialogButtonBox::AcceptRole);
-
+    buttons = new QDialogButtonBox(QDialogButtonBox::Cancel);
+    if (parameters.submit_text.empty()) {
+        buttons->addButton(QDialogButtonBox::Ok);
+    } else {
+        buttons->addButton(QString::fromStdU16String(parameters.submit_text),
+                           QDialogButtonBox::AcceptRole);
+    }
     connect(buttons, &QDialogButtonBox::accepted, this, &QtSoftwareKeyboardDialog::accept);
     connect(buttons, &QDialogButtonBox::rejected, this, &QtSoftwareKeyboardDialog::reject);
     layout->addWidget(header_label);