Fix grammar and clarity in engine API comment

[mdqst]

I addressed a grammatical issue and improved the clarity of a key comment related to the engine API payload builder.

Changes Made:

1. Corrected the verb form from "launch" to "launches" to ensure grammatical agreement with the subject.
2. Added a comma after "node" to improve readability.
3. Clarified the phrase "with our custom" by completing it as "with our custom one."

The revised comment now reads:

//! This launches the regular reth node, overriding the engine API payload builder with our custom one.  

I believe this adjustment improves both readability and accuracy, ensuring the intent is clear for anyone reading or maintaining the code.

[mattsse]

typo fix prs are currently no longer accepted

[codspeed-hq]

CodSpeed Performance Report

Merging #13573 will degrade performances by 10.45%

_{Comparing mdqst:patch-4 (b5acbfa) with main (91dd417)}

Summary

❌ 1 regressions
✅ 76 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	mdqst:patch-4	Change
❌	`hash builder[init size 10000	update size 100	num updates 1]`	9.1 ms

[mdqst]

mattsse, gakonst, I understand that you will most likely not respond to me, but what a foolishness this is. I am trying to improve the project, but my efforts are simply being ignored. You are a very disloyal project.