"Configuring your env" page: `rake secret` is no longer correct, needs to be `bundle exec rails secret`

[umangv]

It looks like the docs need a change similar to this PR from the source code repo.

Under the "secrets" section of the admin/config page, the docs for SECRET_KEY_BASE say:

Generate with rake secret. Changing it will break all active browser sessions.

According to mastodon/mastodon#30917, the command should probably be bundle exec rails secret.

@ciencia also called this out in a separate issue two years ago and I encountered the same problem today. Using bundle exec rails secret worked me.