Remove deprecation comment for protected indices settings

[shikharj05]

Description

[Describe what this change achieves]

• Category (Enhancement, New feature, Bug fix, Test fix, Refactoring, Maintenance, Documentation) - Maintenance
• Why these changes are required? The setting is documented here- https://github.com/opensearch-project/security/blob/main/config/opensearch.yml.example#L214-L221
  This can continue as a feature of security plugin to mark certain indices which can be access by specific plugins.security.protected_indices.roles roles
• What is the old behavior before changes and new behavior after changes?

Issues Resolved

#3190

Is this a backport? If so, please add backport PR # and/or commits #, and remove backport-failed label from the original PR.

Do these changes introduce new permission(s) to be displayed in the static dropdown on the front-end? If so, please open a draft PR in the security dashboards plugin and link the draft PR here

Testing

[Please provide details of testing done: unit testing, integration testing and manual testing]

Check List

• [NA] New functionality includes testing
• [NA] New functionality has been documented
• [NA] New Roles/Permissions have a corresponding security dashboards plugin PR
• [NA] API changes companion pull request created
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.46%. Comparing base (472f7c7) to head (c2bee9d).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5056      +/-   ##
==========================================
- Coverage   71.51%   71.46%   -0.05%     
==========================================
  Files         336      336              
  Lines       22621    22621              
  Branches     3600     3600              
==========================================
- Hits        16177    16167      -10     
- Misses       4645     4654       +9     
- Partials     1799     1800       +1     

Files with missing lines	Coverage Δ
...g/opensearch/security/support/ConfigConstants.java	95.23% <ø> (ø)

... and 7 files with indirect coverage changes