Update link for public shares access_webdav.rst

[JL710]

This PR fixes an old url for public shares. The old url would cause errors in nextcloud when accessing clients like rclone.
I don't know this for sure, but I think the old url got left over from a long time a go and was forgotten to be updated with the other ones.

The developer docs contain the correct link and explanation.

The error that appeared:

OC\Files\FilenameValidator::isForbidden(): Argument #1 ($path) must be of type string, null given, called in /var/www/html/lib/private/Files/View.php on line 1967

[welcome]

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[github-actions]

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