[2.3.0] Checkmk Werk 16769 created: MultipleChoice formspec: use list as default value instead of tuple

[//]: # (werk v2) # MultipleChoice formspec: use list as default value instead of tuple key | value ---------- | --- date | 2024-06-20T06:07:52+00:00 version | 2.3.0p7 class | fix edition | cre component | checks level | 1 compatible | yes During the creation of certain rules with MultipleChoice formspec, the following warning appeared due to default values being saved as a list instead of a tuple: _"Unable to read current options of this rule. Falling back to default values. When saving this rule now, your previous settings will be overwritten. The problem was: [...]: The datatype must be list, but is tuple."_ This werk corrects this behavior by allowing the use of any `Sequence` of strings as values.