Fix incorrect rladmin command in create-certificates.md (Fixes #3737)

[harshh6305]

Fixes #3737

Problem

The "Install certificates" section instructed users to check certificate status using:

rladmin status certificates

This command doesn't work — rladmin has no certificates subcommand, resulting in:

ERROR: invalid token 'certificates'

Fix

Replaced the incorrect command with an openssl x509 command to verify the installed certificate's expiration dates, as suggested in the issue.

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Note

Low Risk
Documentation-only correction; no product code or operational behavior changes.

Overview
Fixes #3737 in the Install certificates section of create-certificates.md.

The post-install step Check certificate status no longer tells users to run rladmin status certificates (invalid rladmin subcommand). It now uses openssl x509 -in /path/to/redis-cert-chain.pem -noout -dates, aligned with the validation section elsewhere in the same doc. The following View certificate details step (rladmin info cluster) is unchanged.

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