Kamal "inlines" calls to `kamal secrets` in the dotenv file, but the
results of the calls were not being escaped properly. To "fix" this
`kamal secrets fetch` escaped the JSON string before returning it.
The two errors cancelled out, but it meant that the commands didn't
work from a shell.
To fix, we'll escape the inline command results and remove the escaping
from `kamal secrets fetch`.
ff24fd9874