[Docs] Clarify Shared file system repository location setting

[a03nikki]

Description

The documentation could be more explicit that the location value is expected to be a single file path, not an array of values.

This has caused user confusion because path.repo is an array of path values but settings.location in a single path value.

location
(Required, string) Location of the shared filesystem used to store and retrieve snapshots. This location must be registered in the path.repo setting on all master and data nodes in the cluster.

Documentation for version 8.8 accessed July 3rd, 2023 from https://www.elastic.co/guide/en/elasticsearch/reference/8.8/snapshots-filesystem-repository.html#snapshots-filesystem-repository.

If one attempts to provide an array of values, it turns into a string used for a new directory created in the first entry of the path.repo value as it is treated as a relative path value.

[elasticsearchmachine]

Pinging @elastic/es-docs (Team:Docs)

[elasticsearchmachine]

Pinging @elastic/es-distributed (Team:Distributed)

[DaveCTurner]

It's a bug that we accept a list here, specifically #33135. Really we should fix this bug, or else we will end up needing to document our way around it for every Setting<String>.