[Style fixes] Intro modal

[jasperjansz]

• 1. Remove Secret Key logo: fixed in Style fixes for modal #49
• 2. Update header font: tracked here -> Update header fonts from Inter to Matter ui#34
• 2.a. It should also be 20px instead of 24px (Header small): fixed in Style fixes for modal #49
• 3. font size for button label should be 14px (body medium) tracked here -> Determine and fix button font size not working ui#36
• 4. Footer links should be 12px (caption medium): fixed in Style fixes for modal #49
• 5. Modal width should be 396px instead of 440px: tracked here -> Update modal width from 440px to 396px ui#35
• 6. padding left and right should be 32px instead of 24px (not applicable to close icon): fixed in Style fixes for modal #49
• 7. The header text should be subject to the same padding. That's 24px (always) on mobile specifically: