Remove temporary/experimental flag --Xsnapsync-bft-enabled

[matthew1001]

Our testing shows that this is stable and hasn't shown any issues since being introduced as an experimental option.

It can be moved out of the experimental options have the X prefix dropped, and be added to the Besu docs. removed entirely

[pullurib]

I can take care of this, please assign

[matthew1001]

@pullurib I think I should have named this "Remove the experimental --Xsnapsync-bft-enabled flag. We added it as a way to turn BFT snap sync on and off while we tested the function. Now that we're happy it works, I think we want to remove the flag entirely, and then I think we can just remove the BesuCommand.validateConsensusSyncCompatibilityOptions() function as well.