Document disableAliases setting

[bep]

See gohugoio/hugo#3613

[stale]

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[bmackinney]

I think this can be closed. The setting is documented at https://gohugo.io/getting-started/configuration/#all-configuration-settings

[kenmorse]

It does seem like this was fixed in commit 8cba70e as part of issue gohugoio/hugo#5722.