docs: update SNYK_HTTP_PROTOCOL_UPGRADE description

Co-authored-by: Jeff McLean <44034094+maxjeffos@users.noreply.github.com>

Author: JackuB

help/commands-docs/_ENVIRONMENT.md

@@ -29,7 +29,7 @@ By default Snyk CLI will connect to `https://snyk.io/api/v1`.
   Sets API host to use for Snyk requests. Useful for on-premise instances and configuring proxies. If set with `http` protocol CLI will upgrade the requests to `https`. Unless `SNYK_HTTP_PROTOCOL_UPGRADE` is set to `0`.
 
 - `SNYK_HTTP_PROTOCOL_UPGRADE`=0:
-  If set to the value of `0` the API requests aimed at `http` URLs will not be upgraded to `https`. Useful e.g., for reverse proxies.
+  If set to the value of `0`, API requests aimed at `http` URLs will not be upgraded to `https`. If not set, the default behavior will be to upgrade these requests from `http` to `https`. Useful e.g., for reverse proxies.
 
 - `HTTPS_PROXY` and `HTTP_PROXY`:
   Allows you to specify a proxy to use for `https` and `http` calls. The `https` in the `HTTPS_PROXY` means that _requests using `https` protocol_ will use this proxy. The proxy itself doesn't need to use `https`.