ref: fix a few type errors in sentry testutils

[asottile-sentry]

fixes some errors when BaseManager becomes typechecked

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.05%. Comparing base (f98a882) to head (cd5b716).
Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #72806       +/-   ##
===========================================
- Coverage   88.20%   78.05%   -10.15%     
===========================================
  Files        2900     6601     +3701     
  Lines      180171   294373   +114202     
  Branches    32214    50753    +18539     
===========================================
+ Hits       158920   229778    +70858     
- Misses      15342    58352    +43010     
- Partials     5909     6243      +334     

Files	Coverage Δ
src/sentry/testutils/factories.py	93.32% <100.00%> (+<0.01%)	⬆️
src/sentry/testutils/pytest/sentry.py	85.11% <100.00%> (+0.06%)	⬆️
...ntry/web/frontend/debug/debug_performance_issue.py	90.90% <100.00%> (ø)

... and 3704 files with indirect coverage changes