v3.15.0

Enhancements:

• Add a globus flows run delete command.

• Add globus gcp update mapped and globus gcp update guest
  to update GCP Mapped and Guest Collections.

• globus gcp create mapped now has an option --public for creating public
  GCP Mapped Collections.

• globus endpoint create and globus endpoint update now allow the use of
  --public/--private with GCP Mapped Collections.