docs: remove stale mint enrollment block from getting started guide

[rh-hemartin]

The getting started guide (docs/guides/getting-started/README.md) still has a "Mint enrollment" step telling users to contact the fullsend team in Slack to enroll their org/repo before they can use fullsend. It also includes a note saying public mint mode is "still in progress" and links PR #1580.

Public mint mode landed in PR #2773 and the hosted mint now defaults to mint.fullsend.sh (#6256). No enrollment is required. The block should be removed and the numbered list renumbered.

Related: #3013 (which flagged this stale reference).

[fullsend-ai-triage]

🤖 Finished Triage · ✅ Success · Started 9:58 AM UTC · Completed 10:01 AM UTC

Commit: 7aa8587 · View workflow run →

[fullsend-ai-triage]

Related issues: #3013 tracks adding AGENTS.md guidance to prevent this class of stale cross-reference from recurring — worth addressing alongside or after this fix.

Proposed test case:

After editing docs/guides/getting-started/README.md:
1. Confirm no references to 'enrollment', 'enroll', or 'contact the fullsend team' remain
2. Confirm the numbered list is sequential (no gaps)
3. Confirm no reference to PR #1580 remains
4. Confirm the page still renders correctly (sidebar_position frontmatter intact)

Note: Per AGENTS.md, when removing content from docs, grep docs/ for other references to the enrollment process or PR #1580 that may also need updating.

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Labels: Documentation fix for the getting-started guide (component/docs). Low priority — stale content, not a production issue. Good first issue due to narrow, well-defined scope.

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Next steps:

• /fs-code — agent creates a PR to implement this issue
• /fs-code <your instruction> — agent implements with your specific guidance