In AboutScreen, remove unnecessary padding and add parallax

[kosenda]

Issue

no issue

Overview (Required)

• I looked at the Figma and removed padding that I thought was unnecessary.
• (Suggestion) I thought it would be a richer UI if we added a parallax to AboutHeader

Movie

Before	After

Detail

I chose 40.dp because the space between the header image and text was 40 in Figma

https://github.com/user-attachments/assets/4babc926-8f8d-47b1-8a95-48471f0703bd

https://www.figma.com/design/XUk8WMbKCeIdWD5cz9P9JC/DroidKaigi-2024-App-UI?node-id=54982-75342&t=l2TqUXx0gVgB367Z-4