Change wgrs to zero-size allocation

[grantfirl]

Description

This small change is part of a larger project to pass NCO's requirements of compiling the UFS with the -check all compiler option. Previously conditionally-allocated arrays in fv3atm (particularly GFS_typedefs and CCPP_typedefs) need to always be allocated (at least to zero size) in order to NOT run into runtime errors with the -check all option (used in DEBUG mode). The only change needed in this repo is related to the vertical velocity (wgrs) variable that was added to physics a while back for the lightning algorithm.

https://github.com/ufs-community/ufs-weather-model/issues/2023

How Has This Been Tested?

This was tested using UFS regression tests on Hera with the -check all compiler option added for Intel.

Checklist:

Please check all whether they apply or not

• [X] My code follows the style guidelines of this project
• [X] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [X] My changes generate no new warnings
• [ ] Any dependent changes have been merged and published in downstream modules

[grantfirl]

This is replaced by https://github.com/NOAA-EMC/GFDL_atmos_cubed_sphere/pull/86, which is targeted at the RRFS release branch. This change will likely NOT need to go to dev/emc.