ref(crons): Make check timeout qs variable name more explicit

[davidenwang]

Got confused looking at this thinking it was checking for missed, changed to be more clear that its for timed out

[codecov[bot]]

Codecov Report

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

Project coverage is 77.85%. Comparing base (c81c348) to head (027f4ac). Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #71307   +/-   ##
=======================================
  Coverage   77.85%   77.85%           
=======================================
  Files        6532     6532           
  Lines      291099   291099           
  Branches    50373    50373           
=======================================
  Hits       226636   226636           
+ Misses      58229    58228    -1     
- Partials     6234     6235    +1     

Files	Coverage Δ
src/sentry/monitors/clock_tasks/check_timeout.py	91.42% <100.00%> (ø)

... and 6 files with indirect coverage changes