Add spec for update of max_issue_count on lists

Failing spec

Rename migration file

Add max_issue_count to schema.rb

Add model validation for max_issue_count

Add license check for max_issue_count

Extract method create_list_attributes

Remove validation for max_issue_count

Add MR to changelog

Remove unnecessary comment

Remove unnecessary allow_null: false

Remove CE changelog entry

Remove possible null value for max_issue_count from schema definitions