Preparing for final Dashing sync and patch release

[tfoote]

Closing the loop, the final sync was announced here:

New packages and patch release for ROS 2 Dashing Diademata 2021-06-10 final

I’m delighted to announce the final sync and patch release for ROS 2 Dashing Diademata. You can find the patch release on GitHub. [ROS 2 Dashing mascot] Dashing was our first long-term support (LTS) release of ROS 2 with a two year support window. During that time we have had 9 patch releases, 20 syncs, and 732 bloom releases! Dashing has grown from 292 packages upon its first release to 621 packages today. Borrowing the pie chart from the Kinetic EOL post we can see Dashing is shown holdin…