docs: Incorrect comment for independent_bid_threshold in SubmissionConfig

[164zheng]

I noticed a potentially misleading comment for the independent_bid_threshold field within the SubmissionConfig struct in crates/rbuilder/src/live_builder/block_output/relay_submit.rs.

rbuilder/crates/rbuilder/src/live_builder/block_output/relay_submit.rs

Lines 107 to 108 in 9a4f6b6

	/// Bids above this value will only go to fast relays.
	pub independent_bid_threshold: U256,

I think the comment should likely be:
/// Bids above this value will only go to independent relays.

This seems to be a minor documentation discrepancy. Clarifying this would help users better understand the configuration and its behavior.
Thanks!