deps: update pyFV3 (new syntax of ddim fields register())

[romanc]

Description

This PR updates the pyFV3 submodule to current develop. In particular, I need PR NOAA-GFDL/pyFV3#156 in pace such that I can unblock NOAA-GFDL/NDSL#535 in NDSL, which is slated for the next (i.e. August) release.

How Has This Been Tested?

All good as long as CI is still green.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas: N/A
• I have made corresponding changes to the documentation: N/A
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included: N/A

[romanc]

all tests pass - ready to merge

[oelbert]

👍