Remove experimental flags related to the EIP 1559

[matkt]

We need to clean the ExperimentalEIPs class by removing this flags

This was configurable when developing the EIP now the values have been defined in the spec and cannot change via a flags without creating a consensus bug issue on the mainnet

@Option(
      hidden = true,
      names = {"--Xeip1559-basefee-max-change-denominator"},
      arity = "1")
  public static Long basefeeMaxChangeDenominator = 8L;

  @Option(
      hidden = true,
      names = {"--Xeip1559-initial-base-fee"},
      arity = "1")
  public static Long initialBasefee = EIP1559_BASEFEE_DEFAULT_VALUE;

  @Option(
      hidden = true,
      names = {"--Xeip1559-slack-coefficient"},
      arity = "1")
  public static Long slackCoefficient = 2L;

[garyschulte]

resolved by https://github.com/hyperledger/besu/pull/2577 and https://github.com/hyperledger/besu/pull/2586