LNURL static QR code does not conform LUD-01

[andrei-21]

Describe the bug LNURL static QR code does not conform LUD-01 fallback scheme. The LIGHTNING parameter is uppercased, but has to be lowercased.

To Reproduce Steps to reproduce the behavior:

1. Go to 'Setting'
2. Click on 'Printable static QR code'
3. The url has LIGHTNING parameter

Expected behavior The url has lightning parameter.

Smartphone (please complete the following information):

• Device: Pixel
• OS: Android

Additional context A similar issue has already appeared, but has been fixed: https://github.com/GaloyMoney/blink-mobile/issues/2520.