docs(migration): Add send_default_pii to data_collection migration section

[ericapisani]

Fixes PY-2800
Fixes #7568

[linear-code]

PY-2800

[github-actions]

Codecov Results 📊

✅ 55242 passed | ❌ 1 failed | ⏭️ 2727 skipped | Total: 57970 | Pass Rate: 95.29% | Execution Time: 150m 2s

📊 Comparison with Base Branch

Metric	Change
Total Tests	📉 -82723
Passed Tests	📉 -78175
Failed Tests	📈 +1
Skipped Tests	📉 -4549

➕ New Tests (1)

View new tests

• test_cache_spans_item_size
  • File: tests.integrations.django.test_cache_module
  • Status: ❌ Failing

❌ Failed Tests

test_cache_spans_item_size

File: tests.integrations.django.test_cache_module
Suite: py3.14t-django-v6.1.1
Error: tests/integrations/django/test_cache_module.py:546: in test_cache_spans_item_size assert not spans[0]["attributes"]["cache.hit"] E assert not True

Stack Trace

tests/integrations/django/test_cache_module.py:546: in test_cache_spans_item_size
    assert not spans[0]["attributes"]["cache.hit"]
E   assert not True

✅ Patch coverage is 100.00%. Project has 2054 uncovered lines.
❌ Project coverage is 90.06%. Comparing base (e7a481c) to head (bbbb165).

Coverage diff

@@            Coverage Diff             @@
##        master       #PR       +/-##
==========================================
- Coverage    90.37%    90.06%    -0.31%
==========================================
  Files          202       185       -17
  Lines        26547     20670     -5877
  Branches      9852      7114     -2738
==========================================
+ Hits         23990     18616     -5374
- Misses        2557      2054      -503
- Partials      1496      1215      -281

---

Generated by Codecov Action

[sentrivana]

Approving to not block, but please check comments