fix: Change env var disabling OpenSearch security plugin

[oelhammouchi]

This closes #772

[alexanderankin]

Can you set both vars for back compat?

[oelhammouchi]

Can you set both vars for back compat?

Unfortunately not, I tested it already and it gives an error:

ERROR: setting [plugins.security.disabled] already set, saw [true] and [true]

However, the change seems backwards compatible by itself, as the tests still pass.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (main@b1642e9). Learn more about missing BASE report.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #773   +/-   ##
=======================================
  Coverage        ?   84.73%           
=======================================
  Files           ?       12           
  Lines           ?      668           
  Branches        ?      105           
=======================================
  Hits            ?      566           
  Misses          ?       79           
  Partials        ?       23           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.