Use LAPLACIAN = False in tx2_3v2

[gustavo-marques]

MOM_interface always sets LAPLACIAN = True (see here). However, in the workhorse configurations (tx2_3v2), the Laplacian coefficient is zero, so setting LAPLACIAN = True has no effect.

Let's set LAPLACIAN = False for the tx2_3v2 configurations to avoid confusion, which will not change the answers.