docs: fix broken links

[jcstein]

## Errors per input

### Errors in .vitepress/config.ts

* [TIMEOUT] [https://t.me/CelestiaCommunity](https://t.me/CelestiaCommunity) | Timeout

### Errors in how-to-guides/participate.md

* [502] [https://t.me/+smSFIA7XXLU4MjJh](https://t.me/+smSFIA7XXLU4MjJh) | Network error: Bad Gateway

### Errors in how-to-guides/arabica-devnet.md

* [TIMEOUT] [https://t.me/+smSFIA7XXLU4MjJh](https://t.me/+smSFIA7XXLU4MjJh) | Timeout

Error: Process completed with exit code 2.