clean up SMART docs a bit

[VVelox]

Clean up the docs... don't mention trying to use sudo, use -Z, and only document doing it via cron.

• -Z is pretty much required as more complex JSON tends to freak snmpd the hell out but snmpd is very happy with base64.
• Can work via sudo, but more things to go wrong, but more likely to not work than work thanks to disk polling time for SMART.
• Print cache via cat for the sake of simplicity.

DO NOT DELETE THE UNDERLYING TEXT

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[librenms-bot]

This pull request has been mentioned on LibreNMS Community. There might be relevant details there:

https://community.librenms.org/t/24-6-0-changelog/24707/1