release update for 4.7.6 and removed Centos8

[ValClarkson]

release update for 4.7.6 and removed Centos8 from documents, examples, and Makefile

[sc-14635]

Checklist:

• [ ] Have you added an explanation of what your changes do and why you'd like them to be included?
• [x ] Have you updated or added documentation for the change, as applicable?
• [ ] Have you tested your changes on all related environments with successful results, as applicable?

Type of Changes:

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

What is the current behavior? (link to any open issues here)

What is the new behavior (if this is a feature change)?

Other information: