Feature Definition Freeze THIS Thursday (06/18)

[Robbie Williamson]

https://wiki.ubuntu.com/FeatureDefinitionFreeze

All features with updates to be landed in main for the release must be named and
acked by the ReleaseTeam. Having this freeze gives them a chance to identify any
features which should be subject to an earlier NewPackageUploadDeadline or
FeatureFreeze deadline because they are especially risky.