[Documentation] Update GitHub description, README, etc to reflect new CNTI Certification program

[lixuna]

Describe the update:

• Update GitHub description, README, etc to reflect new CNTI program
• https://wiki.lfnetworking.org/display/LN/Certification

Describe why update is needed

• CNF WG (and CNCF’s related Cloud Native Telco efforts) has moved to LFN (see wiki)
• The certification used to be called CNF Certification
• The certification is currently called CNTI Certification

Additional context

• https://wiki.lfnetworking.org/pages/viewpage.action?pageId=113213592

• 61

• Remove references to CNCF and CNCF Certification in documentation

Tasks:

• [x] update description
• [x] update https://github.com/lfn-cnti/certification/blob/main/README.md
• [ ] tbd

[lixuna]

✅ Description has been updated:

[lixuna]

👍 README updates are Ready for Peer review - PR #86