Remove coco and ssd

[growlix]

What does this PR do?

This PR removes COCO and SSD due to lack of use and maintenance. Deyahpification seemed like a good opportunity to pull the plug. From the relevant ticket:

I’m not sure if it would be worth the time to deyahpify COCO since it may not be easy to test. The only model that can use it is SSD, but no one has used this for sometime so it may not work. In the future, I think we want to move to pulling models from mmdetection which will likely require the COCO to be refactored to output a different data structure. Since we anticipate a refactor in the future, it may be worth delaying the deyahp until then.

Before submitting

• Have you read the contributor guidelines?
• Is this change a documentation change or typo fix? If so, skip the rest of this checklist.
• Was this change discussed/approved in a GitHub issue first? It is much more likely to be merged if so.
• Did you update any related docs and document your change?
• Did you update any related tests and add any new tests related to your change? (see testing)
• Did you run the tests locally to make sure they pass?
• Did you run pre-commit on your change? (see the pre-commit section of prerequisites)

[A-Jacobson]

I'm cool with it. 100% agree with what you quoted. Did i say that?

[karan6181]

LGTM. Thanks!

[Landanjs]

LGTM! Another 1.3k LOC down