Need to convert RRTMGP externals to submodules with depth=1

[nusbaume]

Issue Type

Externals Update

Issue Description

Once PR #909 has been merged, and PR #946 is out-of-draft, then it would be great to make sure that the two RRTMGP externals (rte-rrtmgp and rrtmgp-data) are brought in as shallow submodules with a depth of one. This will allow CAM to significantly reduce the size of a checkout while still acquiring all of the necessary files needed for radiation.

Pinging @cacraigucar @jedwards4b @brian-eaton as a heads-up.

Will this change answers?

No

Will you be implementing this yourself?

Any CAM SE can do this

[jedwards4b]

My plan will be to bring in all of the submodules using this method in PR #946.

[nusbaume]

Great, thanks @jedwards4b! I'll leave this issue open for now just so us CAM SEs will remember that git-fleximod will fix our current repo size issue.

[cacraigucar]

Done with git-fleximod