Update reference link for [ZFS/en] ZFS tuning guide

The ZFS article page is awesome, with plenty of clear explanations and a handful of resources at the end. The ZFS article has a link to the ZFS tuning guide from the OpenZFS guide. But it seems the page has been moved and is out of date on the website.

The new OpenZFS tuning guide is referenced here:
(https://openzfs.github.io/openzfs-docs/Performance%20and%20Tuning/Workload%20Tuning.html)

However, the learnxinyminutes references it to the old page. Please add it as an update.

Locate the ZFS article source file in this repository and the resource section with the OpenZFS tuning guide link. Start by searching for the old OpenZFS guide URL or the phrase "Performance and Tuning" to find the exact markdown line. Replace that link with the new URL from the issue, then check the updated article renders with the new link target.

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