Update RC4 tag descriptions to include equivalent dev tags

[astrogeco]

Checklist (Please check before submitting)

• [x] I reviewed the Contributing Guide.
• [x] I reviewed the cFS README.md file to see if the feature is in the major future work.
• [x] I performed a cursory search to see if the feature request is relevant, not redundant, nor in conflict with other tickets.

Is your feature request related to a problem? Please describe.

Need a mapping between tags and build numbers to reduce confusion

Describe the solution you'd like Include RC information in update history on readme and tag description

Describe alternatives you've considered Finish official release and add official numbers

Additional context Raised in stakeholder meeting

Requester Info @astrogeco