Clarified description of when the vulnerability was created per https://github.com/CycloneDX/specification/pull/91#discussion_r721860406
Clarified description of when the vulnerability was created per https://github.com/CycloneDX/specification/pull/91#discussion_r721860406

Signed-off-by: Steve Springett <9ce5770b3bb4b2a1d59be2d97e34379cd192299f@springett.us>

CycloneDX/specification,CycloneDX/specification,CycloneDX/specification,CycloneDX/specification,CycloneDX/specification