Invalid sequence schema for menu_token.availableentitiesconfiguration: available_entities

Problem/Motivation

Use YAML list syntax instead of a mapping, so each element is typed as undefined.
Config Inspector reports one error per stored entity machine name (e.g. 16 errors on a typical site).

Steps to reproduce

Proposed resolution

Change - type: string to type: string in config/schema/menu_token.schema.yml.

Remaining tasks

User interface changes

API changes

Data model changes