Cleanup md files

[cliu123]

opensearch-security pull request intake form

Please provide as much details as possible to get feedback/acceptance on your PR quickly

1. Category: (Enhancement, New feature, Bug fix, Test fix, Refactoring, Maintenance, Documentation)
   Maintenance

2. Github Issue # or road-map entry, if available:
   Level up README and related markdown content #1297

3. Description of changes:

4. Why these changes are required?

5. What is the old behavior before changes and new behavior after changes? (Please add any example/logs/screen-shot if available)

6. Testing done: (Please provide details of testing done: Unit testing, integration testing and manual testing)

7. TO-DOs, if any: (Please describe pending items and provide Github issues# for each of them)

8. Is it backport from main branch? (If yes, please add backport PR # and commits #)

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[codecov-commenter]

Codecov Report

Merging #1298 (098aa8b) into main (4abbafc) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##               main    #1298   +/-   ##
=========================================
  Coverage     64.73%   64.73%           
- Complexity     3194     3195    +1     
=========================================
  Files           247      247           
  Lines         17230    17230           
  Branches       3045     3045           
=========================================
  Hits          11153    11153           
  Misses         4528     4528           
  Partials       1549     1549           

Impacted Files	Coverage Δ
...a/org/opensearch/security/tools/SecurityAdmin.java	47.39% <0.00%> (-0.14%)	⬇️
.../dlic/auth/ldap2/LDAPConnectionFactoryFactory.java	58.01% <0.00%> (+0.76%)	⬆️

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[dblock]

This looks good, we'll need to update ADMINS with recommendations from @CEHENKLE.