[FEATURE] Update instances of admin:admin in Security

[derek-ho]

Is your feature request related to a problem?
https://github.com/search?q=org%3Aopensearch-project+admin%3Aadmin+++repo%3Aopensearch-project%2Fsecurity&type=code

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[peternied]

Looks like this is a duplicate of line items on the meta issues associated with default password