DX: Tweak comments in redwood.toml

[Tobbe]

I always get insecure about the array syntax in the toml for listing env vars. Like, am I allowed to have newlines?
Hopefully adding the comments on new lines inside the array makes it clear that you're allowed to do that.

Ideally I'd like the comment to say:

Add ENV_VARs each on their own line. Quote the variable name and end the line with a comma (,). Like this:
'EXAMPLE_VAR_ONE',
'EXAMPLE_VAR_TWO',

I figured that was too long, but happy to take suggestions on how to further improve the wording in the PR

[ahaywood]

LGTM