[DASH-639] Remove unused assets (#5759)

## Problem solved

Short description of the bug fixed or feature added

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## PR-Codex overview
This PR focuses on the deletion of numerous image files from various directories within the `apps/dashboard/public/assets` folder, including images related to partners, ambassadors, landing pages, and grants.

### Detailed summary
- Deleted multiple image files from `partners`, `ambassadors`, `landingpage`, `community`, and `grant` directories.
- Removed images such as `aws.png`, `polygon.png`, `coinbase.png`, `superchain/logo-dashboard.png`, and many others.
- A total of 160 image files were deleted.

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