[Will Be Closed With #55] Add support for 4-channel CMYK encoded images

[ndushay]

Why was this change made? 🤔

@calavano is this ready to be a PR?

• would we want to add a CMYK image in the test data and create a spec to test this?
• would we want to perform some other kind of automated test? (e.g. add data and a test in common-accessioning code?)
• or has this gotta be tested with a person/

How was this change tested? 🤨

⚡ ⚠ If this change has cross service impact, run integration tests that do IMAGE ACCESSIONING (e.g. create_preassembly_image_spec) and/or test in [stage|qa] environment, in addition to specs. ⚡

[calavano]

@ndushay This was a old branch (2019) that would have worked with ImageMagick. With the intended move to libvips, it would probably be a better idea to delete this branch.

[ndushay]

this is no longer needed as our switch to libvips got CMYK images with 4 channels working.