[QoS Booking And Assignment] Defined example BOOKING_FAILURE is unused

[eric-murray]

Problem description
Example BOOKING_FAILURE is defined in the OAS definition, but not used.

Expected action
Use it or delete it

Additional context
This is a validation warning:

code/API_definitions/qos-booking-and-assignment.yaml:1738:21 — [S-211] Potentially unused component has been detected.

[Masa8106]

This issue was addressed in merged PR (#139). So this issue should be closed.