Docs of backend.exists() wrongly state that error is raised if path does not exist

[hagenw]

In the documentation of audbackend.Backend.exists() it is stated

This feels strange, and it is also not the case:

import audbackend

backend = audbackend.access('artifactory', 'https://audeering.jfrog.io/artifactory', 'data-public')
backend._use_legacy_file_structure()

>>> backend.exists(backend.join('/', 'emodb', 'db.yaml'), '1.4.1')
True

>>> backend.exists(backend.join('/', 'non-existing', 'db.yaml'), '1.0.0')
False

[frankenjoe]

Yes, we should replace e.g. path does not exist with e.g. due to a connection error