Make OSLC-Core-Version permanent

[berezovskyi]

• Field name: OSLC-Core-Version
• Status: permanent
• Specification document(s): https://docs.oasis-open-projects.org/oslc-op/core/v3.0/os/oslc-core.html
• Comments: in the discussion of our previous request we agreed to make it provisional until the OASIS Standard is published. OSLC Core Version 3.0 became an OASIS Standard on 26 August 2021.

Thank you!