Update the category maturity target for the container registry

Why is this change being made?

The Package group kicked off a series of maturity target reviews where the team will review the maturity target for a given category and evaluate if anything is missing or needs to be updated.

Well, the first category was the container registry and given the timeline for deploying and migrating the registry on GitLab.com, distribution to self-managed, and the list of features required to reach the target, the team decided that February 2022 is not realistic and that July 2022 is.

So this MR updates the category maturity target.

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