docs: provide information for SENTRY_AIR_GAP flag on Django config file

[aldy505]

Corresponding PR: getsentry/sentry#99281

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.49%. Comparing base (84f904f) to head (9d9e1a4).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3935   +/-   ##
=======================================
  Coverage   99.49%   99.49%           
=======================================
  Files           3        3           
  Lines         197      197           
=======================================
  Hits          196      196           
  Misses          1        1           

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[aminvakil]

@aldy505 I think you wanted a review from someone else and asked me by mistake again.

[aldy505]

@aldy505 I think you wanted a review from someone else and asked me by mistake again.

No, that was a race condition. You approve before I re-requested the review.