Update externals to match externals which will be used in cesm2_3_beta18

[cacraigucar]

Issue Type

Externals Update

Issue Description

In order to enable the tag with the git-fleximod changes to bit-for-bit, we need to update our externals to what will be used in cesm2_3_beta18.

Will make sure this fixes #1004

Will this change answers?

Yes

Will you be implementing this yourself?

Yes