[Misc] Fix links to the CTA developer docs

Description

This MR:

• Renames any links still referring to eoscta.docs.cern.ch to cta.docs.cern.ch
• Fixes some broken links

Checklist

• Documentation reflects the changes made.
• Merge Request title is clear, concise, and suitable as a changelog entry. See our contributing docs

References

Closes #1285 (closed)