ref(crons): Remove crons issue platform flag

[rjo100]

Removes flag as feature is live in production

[codecov]

Codecov Report

Merging #51291 (3df2709) into master (cd475eb) will increase coverage by 0.64%.
The diff coverage is 93.61%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #51291      +/-   ##
==========================================
+ Coverage   80.57%   81.22%   +0.64%     
==========================================
  Files        4891     4893       +2     
  Lines      205011   205040      +29     
  Branches    11107    11107              
==========================================
+ Hits       165186   166534    +1348     
+ Misses      39579    38260    -1319     
  Partials      246      246              

Impacted Files	Coverage Δ
src/sentry/conf/server.py	91.63% <ø> (ø)
src/sentry/monitors/models.py	94.29% <ø> (ø)
static/app/views/alerts/rules/issue/index.tsx	76.09% <ø> (ø)
src/sentry/integrations/discord/integration.py	90.47% <90.47%> (ø)
src/sentry/monitors/consumers/monitor_consumer.py	92.25% <92.85%> (-3.93%)	⬇️
src/sentry/features/__init__.py	100.00% <100.00%> (ø)
src/sentry/integrations/discord/__init__.py	100.00% <100.00%> (ø)
...nitors/endpoints/monitor_ingest_checkin_details.py	90.90% <100.00%> (+0.52%)	⬆️
src/sentry/monitors/utils.py	98.24% <100.00%> (+0.20%)	⬆️
src/sentry/monitors/validators.py	95.45% <100.00%> (ø)

... and 88 files with indirect coverage changes

[getsentry-bot]

PR reverted: a1226f9