Missing MOM6_VERTICAL_GRID setting in tx2_3v3

[gustavo-marques]

In #318, a definition for MOM6_VERTICAL_GRID was not included, and the system chose the default option, zstar_65L. We need to add the following in the MOM6_VERTICAL_GRID entry:

<value grid="oi%tx2_3v3">hycom1</value>