OpenAPI schema fixes blocking openapi-typescript

[cconard96]

Checklist before requesting a review

• I have read the CONTRIBUTING document.
• I have performed a self-review of my code.

Description

I use openapi-typescript to automatically generate TypeScript types from the GLPI API schema for my project and two issues were blocking the type generation.

• CalendarCloseTime was a non-existent schema name which was adding endpoints that were broken.
• The default endpoints were adding a "content" property for an empty schema which is not valid OpenAPI syntax.