chore: remove enrollment button snippet

[jxnl]

Important

Remove enrollment-button.md snippet from various markdown files across the project for documentation cleanup.

• Documentation Cleanup:
  • Removed enrollment-button.md snippet from README.md, cohort_1/README.md, and cohort_2/README.md.
  • Removed enrollment-button.md snippet from various week directories in cohort_1 and cohort_2.
  • Removed enrollment-button.md snippet from docs/blog.md, docs/office-hours/AGENTS.md, and docs/talks/AGENTS.md.
• Misc:
  • Removed enrollment-button.md snippet from latest/README.md and latest/week0/README.md.
  • Removed enrollment-button.md snippet from md/extra_kura_01_cluster_conversations.md and md/extra_kura_02_better_summaries.md.

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[gitnotebooks]

Review these changes at https://app.gitnotebooks.com/567-labs/systematically-improving-rag/pull/63