docs: fix the example of local PVC based cluster

[satoru-takeuchi]

Description of your changes:

PV for mon must be a filesystem volume.

Which issue is resolved by this Pull Request:
Resolves #8818

Checklist:

• [o] Commit Message Formatting: Commit titles and messages follow guidelines in the developer guide.
• [o] Skip Tests for Docs: Add the flag for skipping the build if this is only a documentation change. See here for the flag.
• [o] Skip Unrelated Tests: Add a flag to run tests for a specific storage provider. See test options.
• [o] Reviewed the developer guide on Submitting a Pull Request
• [o] Documentation has been updated, if necessary.
• [o] Unit tests have been added, if necessary.
• [o] Integration tests have been added, if necessary.
• [o] Pending release notes updated with breaking and/or notable changes, if necessary.
• [o] Upgrade from previous release is tested and upgrade user guide is updated, if necessary.
• [o] Code generation (make codegen) has been run to update object specifications, if necessary.

[mergify]

This pull request has merge conflicts that must be resolved before it can be merged. @satoru-takeuchi please rebase it. https://rook.io/docs/rook/latest/development-flow.html#updating-your-fork

[inouekazu]

Question about Rook/Ceph conventions: I've confirmed that there is no need to separate StorageClasses [1], but is it customary not to separate them, e.g. local-storage-mon, local-storage-osd?

[1] https://github.com/kubernetes/kubernetes/blob/master/pkg/scheduler/framework/plugins/volumebinding/binder.go#L829
[1] https://alibaba-cloud.medium.com/kubernetes-persistent-storage-process-97372f86089d (FindBestMatchPVForClaim:)

[satoru-takeuchi]

@inouekazu No, there is no such convention.