[test] Remove begin/end from constructors to fix morty ci err

[viv-eth]

This PR refactors the AXI module constructors in test/tb_axi_dw_pkg.sv by removing redundant begin...end blocks. The primary objective is to streamline the constructor definitions to account for parser errors occurring in the sv-parser crate used by morty.

• The removal addresses parsing issues related to super.new(...) calls, ensuring that the sv-parser can accurately interpret method calls without being constrained by unnecessary block delimiters.
• The begin...end blocks within constructors were redundant, as the constructor's logic doesn't require multiple procedural statements that necessitate such blocks.

The functional behavior and RTL characteristics of the AXI module remain unchanged. The constructor continues to initialize and configure module parameters as intended.