docs: remove blockspace race testnet Celestia

[jcstein]

This PR removes an old testnet that is no longer live for Celestia. cc @Bidon15

[reversesigh]

This is a good chance to actually fix up the testnet situation with celestia on here.

Instead of completely removing, I suggest:

The folder that is currently labeled testnets/celestiatestnet3 needs to be renamed testnets/celestiatestnet. Sidenote - I don't think Mocha was a fork of anything, but if it was then we'll add "pre_fork_chain_name": "celestiatestnet3". If it was a new launch with a new genesis and from block 1 then ignore adding that field.

I only joined Celestia during Mocha so i can't speak what was before, but if blockspace race was the testnet before mocha, then rename the blockspace race testnet folder to celestiatestnet3 and change the status to killed and change the chain_name to celestiatestnet3. Also delete the images folder for this.

[JeremyParish69]

I think it might be better to reassign the chain_ids for the celestia testnets in a separate PR (celestiatestnet3 -> celestiatestnet, and celestiatestnet -> celestiatestnet1)

[JeremyParish69]

PR has been abandoned.

[jcstein]

will open a new PR for this