Fixes VELA_ADDR example to include https (#63)

This is the observed behavior on my company's internal Vela server.

Co-authored-by: David May <49894298+wass3rw3rk@users.noreply.github.com>

Author: colindean

docs/reference/environment/variables.md

@@ -108,7 +108,7 @@ The following table includes variables only available when the step `id_request`
 | Key                    | Value                                             | Explanation                                                         |
 | ---------------------- |---------------------------------------------------|---------------------------------------------------------------------|
 | `VELA`                 | `true`                                            | environment is Vela                                                 |
-| `VELA_ADDR`            | `vela.example.com`                                | fully qualified domain name of the Vela server                      |
+| `VELA_ADDR`            | `https://vela.example.com`                        | fully qualified domain name of the Vela server                      |
 | `VELA_CHANNEL`         | `vela`                                            | queue channel the build was published to                            |
 | `VELA_DATABASE`        | `postgres`                                        | database Vela is connected to                                       |
 | `VELA_HOST`            | `vela-worker-1`                                   | fully qualified domain name of the worker the build was executed on |