It is not clear that the console command runs in legacy JSON mode by
default and that users can specify the -config-type flag to toggle HCL2
mode. This change adds the config-type flag to the command's help text
to alert users of the gotcha.
In the next minor Packer release the console command will be updated to
default to HCL2 mode.
Relates to: #12359
Relates to: #10603