tests/different-inputs.t is outdated and unused

[victorlin]

I came across this and did some historical digging.

• This test file was added in 20b7564.
• There is another test file, tests/sanitize-metadata.t, which is used by CI as of d60cf1b.

I was unable to run this test locally because:

1. The input data files aren't available in the repo and I don't know how to get them. EDIT: nevermind, I see they're references to files on S3.
2. The workflow config file uses inputs[].filtered, which was formally removed in 2625374.

Possible approaches

1. Rework this test so it is up to date and actively used.
2. Remove the test and supporting files.

[jameshadfield]

Wow, I have almost zero memory of writing these tests. It does cover some general entry points to the pipeline which are good to include in CI, so I'd vote to add to CI if it's simple to do so.