docs: Bring back intersphinx

[sentrivana]

Working again 👀 https://github.com/getsentry/sentry-python/actions/runs/36858760688/job/110357509876?pr=7814

This reverts commit e899330.

[github-actions]

Codecov Results 📊

✅ 132858 passed | ⏭️ 7220 skipped | Total: 140078 | Pass Rate: 94.85% | Execution Time: 448m 51s

📊 Comparison with Base Branch

Metric	Change
Total Tests	📈 +65
Passed Tests	📈 +65
Failed Tests	—
Skipped Tests	—

All tests are passing successfully.

✅ Patch coverage is 100.00%. Project has 2562 uncovered lines.
❌ Project coverage is 90.34%. Comparing base (e899330) to head (150efa6).

Coverage diff

@@            Coverage Diff             @@
##        master       #PR       +/-##
==========================================
- Coverage    90.37%    90.34%    -0.03%
==========================================
  Files          199       199         —
  Lines        26526     26526         —
  Branches      9866      9866         —
==========================================
+ Hits         23971     23964        -7
- Misses        2555      2562        +7
- Partials      1495      1495         —

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