feat: fix little icon (#1174)

### TL;DR

Updated application icons for the code app with new design and simplified icon assets.

### What changed?

- Replaced the existing app icon files (app-icon.icns, app-icon.ico, app-icon.png) with new versions
- Removed the icon.icon directory containing the SVG source file and JSON configuration
- Added a new simplified icon.png file

Author: k11kirky