Fast option in eth_sendPrivateTransaction doesn't work

**Describe the bug**
Hopefully, this is the right repository. I also didn't get attention in the discord channel.
According to the [docs](https://docs.flashbots.net/flashbots-auction/advanced/rpc-endpoint#eth_sendprivatetransaction), to `eth_sendPrivateTransaction` there's an option to specify the "fast" option. I specified this in the request but it's not working.

I'm not sure if I'm actually supposed to be there or not, but it's really confusing. This parameter is also supported in: https://github.com/metachris/flashbotsrpc/blob/master/types.go#L435. This package is used by flashbots here: https://github.com/flashbots/rpc-endpoint/blob/main/server/request_processor.go#L312, but all the builders are fetched instead of specifying fast to the RPC which makes me think even more that it's a bug and this option shouldn't appear in the docs.

**Screenshots**

Start with the eth_sendPrivateTransaction documentation and compare its fast option with request_processor.go and types.go, which the issue links. Trace whether fast is passed through or whether all builders are fetched, then confirm that the implementation matches the documented behavior or that the documentation no longer promises the option.

Written by the indexing model from the issue text.