Rename scheduled_slot_count field to lesson_quota for consistency

...imebound_course_config/TimeboundCourseConfigCRUDTable.vue

...s/timebound_course_config/TimeboundCourseConfigRaster.vue

...nts/timebound_course_config/timeboundCourseConfig.graphql

aleksis/apps/lesrooster/frontend/messages/de.json

aleksis/apps/lesrooster/frontend/messages/en.json

...cheduled_slot_count_timeboundcourseconfig_lesson_quota.py

aleksis/apps/lesrooster/models.py

aleksis/apps/lesrooster/schema/timebound_course_config.py