document configuring SELinux for Shibboleth

[donsizemore]

What this PR does / why we need it:

Update documentation on configuring SELinux for use with Shibboleth

Which issue(s) this PR closes:

• Closes #10193

Special notes for your reviewer:

None

Suggestions on how to test this:

Enable Shibboleth, run provided commands

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