Improve documentation on `UndefinedBehaviorInfo::ValidationFailure`
Improve documentation on `UndefinedBehaviorInfo::ValidationFailure`

aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust