[charms] Trilio Charms 21.03 release is now available

The 21.03 release of the Trilio charms is now available. Please see the Release Notes for full details: https://docs.openstack.org/charm-guide/latest/2103_Trilio.html == Highlights == * TrilioVault 4.1 The charms now support TrilioVault release 4.1. * OpenStack Ussuri The charms add support for OpenStack Ussuri on both Ubuntu 18.04 LTS (Bionic) and Ubuntu 20.04 LTS (Focal). This is in addition to current Bionic support for OpenStack Queens, Stein, and Train. == Thank you == Lots of thanks to the following people who contributed to this release via code changes, documentation updates and testing efforts. Alex Kavanagh Aurelien Lourot Chris MacNaughton David Ames Liam Young Marian Gasparovic Peter Matulis -- OpenStack Charms Team