Changes to Create a media timings set

changed the pattern of the request property metadata/ad_timings/timings/items/timecode from ^(?!00:00:00:000)[0-2][0-3]:[0-5][0-9]:[0-5][0-9].[0-9]{3}$ to ^(?!00:00:00\.000)([01]\d|2[0-3]):([0-5]\d):([0-5]\d)\.(\d{3})$

the allOf[#/components/schemas/TimingMetadata]/metadata/ad_timings/timings/items/timecode response's property pattern was changed from ^(?!00:00:00:000)[0-2][0-3]:[0-5][0-9]:[0-5][0-9].[0-9]{3}$ to ^(?!00:00:00\.000)([01]\d|2[0-3]):([0-5]\d):([0-5]\d)\.(\d{3})$ for the status 201