Old message:
read-only token in GH_TOKEN cannot be modified
This message was vague and some users did not understand that this
refers to the value that is read from environment variables.
New message:
$ GH_TOKEN=123 ghd auth login -h github.com
The value of the GH_TOKEN environment variable is being used for authentication.
To have GitHub CLI store credentials instead, first clear the value from the environment.
