update tbot init error message

[stevenGravy]

Updates error message to be more specific that a destination dir must be configured or parameter to match the specified init dir.

If a user had no config file they get

$ tbot init --init-dir /tmp/test
ERROR: Could not find specified destination /tmp/test

This isn't clear it's looking for the dest dir as a config not whether the dir exists on the file system.

Updated to

ERROR: Initial directory "/tmp/test" must match a destination directory from the configuration file or --destination-dir parameter