[2.2] Updating some URLs from 2.1/master to 2.2

Hi guys!

On a few places, we mention the specific current version for one reason or another. This replaces old 2.1 or master references with "2.2".

After merge, I'll also update a few of the "2.1" references on the master branch to say "master". The idea is that master is always master, and when we create new release branches, we change master to whatever the current version is in these places.

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | no

Thanks!