Removed camera constraints from QR scanner

By default camera needs to be at least 640x640 but I don't see why that's necessary.

Fixes #285

client/src/components/qrCodeScanner.tsx

@@ -27,6 +27,9 @@ const QRCodeScannerModal: React.FC = () => {
         <Space direction="vertical" style={{ width: "100%" }}>
           <p>{t("scanner.description")}</p>
           <QrScanner
+            constraints={{
+              facingMode: "environment",
+            }}
             viewFinder={
               lastError
                 ? () => (