fix: removes the -t argument from imposter down.

[zzcgumn]

No description provided.

[outofcoffee]

Thanks for raising this, @zzcgumn — you correctly spotted that imposter down no longer accepts -t.

I've pushed a follow-up commit to this branch to round out the fix. The recent imposter-cli change didn't just drop the flag, it reworked the command's interface: down now takes a positional mock ID, or --all:

imposter down [ID]
imposter down --all

So imposter down ${{ inputs.engine-type }} passes the engine type as a positional argument, and the CLI treats it as a mock ID — e.g. imposter down docker exits with no managed mock found with ID "docker".

Since the action doesn't track individual mock IDs, the follow-up uses imposter down --all, which stops every managed mock regardless of engine type, matching the previous behaviour. While there I also:

• marked the engine-type input as deprecated and log a warning if it's still set (it no longer affects down);
• dropped its docker default, as it's now unused;
• updated the README to match.

start-mocks keeps engine-type unchanged, since imposter up and imposter engine pull still use it.