chore(features): cleanup feature flags grouped by its' category

[aldy505]

As a follow up for #3837 (comment)

[aldy505]

@evanpurkhiser I removed the feature flags for uptime issue platform & sentry option for write uptime results to snuba. Hoping you can review & approve if I'm correct.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.45%. Comparing base (84d0d23) to head (b04327d).
⚠️ Report is 3 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3843   +/-   ##
=======================================
  Coverage   99.45%   99.45%           
=======================================
  Files           3        3           
  Lines         183      183           
=======================================
  Hits          182      182           
  Misses          1        1           

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[evanpurkhiser]

Yep it's safe to remove the uptime flags

[evanpurkhiser]

Will leave it to someone else to approve.