[2.3.0] Checkmk Werk 16636 created: check_mailboxes: fix issue with EWS distinguished folder

[//]: # (werk v2) # check_mailboxes: fix issue with EWS distinguished folder key | value ---------- | --- date | 2024-05-15T07:47:43+00:00 version | 2.3.0p3 class | fix edition | cre component | checks level | 1 compatible | yes The active check "check_mailboxes" could fail with a `KeyError: 'folders'` when trying to retrieve an exchange mailbox's folders via the EWS protocol. With this werk the used library `exchangelib` is updated to v5.4.0, which prevents the underlying issue in retrieving certain exchange folders.