ref(tests): Add event_type to store_event

[ceorourke]

Unless you add stacktrace information to data, events are created as the "default" type rather than error. This trips me up all the time when I expect them to be "error" type by default, so hopefully adding this should help others not have the same pitfall.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 77.85%. Comparing base (a8e8282) to head (fea4fc2). Report is 62 commits behind head on master.

:exclamation: Current head fea4fc2 differs from pull request most recent head 8c2027a

Please upload reports for the commit 8c2027a to get more accurate results.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #71306   +/-   ##
=======================================
  Coverage   77.85%   77.85%           
=======================================
  Files        6532     6533    +1     
  Lines      291096   291140   +44     
  Branches    50372    50379    +7     
=======================================
+ Hits       226635   226670   +35     
- Misses      58221    58233   +12     
+ Partials     6240     6237    -3     

Files	Coverage Δ
src/sentry/testutils/factories.py	93.28% <100.00%> (+0.02%)	:arrow_up:
src/sentry/testutils/pytest/fixtures.py	81.01% <ø> (-0.12%)	:arrow_down:

... and 27 files with indirect coverage changes