repos/builtin/ submodule update (py-mpi4py)

[AlexanderRichert-NOAA]

Description

This PR brings in the py-mpi4py update (CXX dependency). No configuration changes needed, just doing this for CI testing.

Dependencies

JCSDA/spack-packages#15

Issues addressed

none

Applications affected

GW, probably others

Systems affected

all

Testing

• CI: Note whether the automatic tests (GitHub actions tests that run automatically for every commit) pass or not
  • GitHub actions CI tests pass
• Additional testing: Add information on any additional tests conducted
  • Tested on Acorn

Checklist

• This PR addresses one issue/problem/enhancement or has a very good reason for not doing so.
• These changes have been tested on the affected systems and applications.
• All dependency PRs/issues have been resolved and this PR can be merged.
• All necessary updates to the documentation on readthedocs are included in this PR
• All necessary updates to the spack-stack wiki will be made when this PR is merged

[climbfuji]

@AlexanderRichert-NOAA I think we can close this. The submodule pointer update for spack-packages is done in #1798