CHECKOUT_code typo

[laurenchilutti]

Describe the bug
The GitHub repo for FMScoupler is https://github.com/NOAA-GFDL/FMScoupler. We have been checking this out as https://github.com/NOAA-GFDL/FMSCoupler (capital C). For consistency I would like to change our capitalization to match the repository's real name.

To Reproduce
Look at code

Expected behavior
Everything works fine

System Environment
N/A

Additional context
N/A