OdumInstitute is now UNCCH-RDMC

[donsizemore]

What this PR does / why we need it:

Update guides_build_sphinx.yml to avoid calling an old GitHub org which may be reclaimed in time.

Which issue(s) this PR closes:

• Closes #10218

Special notes for your reviewer:

None

Suggestions on how to test this:

Update guides in some way, optimally in a branch.

Does this PR introduce a user interface change? If mockups are available, please link/include them here:

no

Is there a release notes update needed for this change?:

no

Additional documentation:

none