Bump OrderedCollections compat to include v2

[asinghvi17]

No description provided.

[oxinabox]

Hmm because we reexport OrderedCollections.
a breaking change there is probably also a breaking change here.
I failed to think this through or I would have synconized the OrderdCollections 2.0 release with the DataStructures 0.19 release.

Have to think what do do here.
@timholy do you have thoughts?

[bluesmoon]

In terms of breaking changes, can I just note that the code that was removed in OrderedCollections 2.0.0 has been deprecated since the release of OrderedCollections 1.0.0 which was 8 years ago. This was also the second release of OrderedCollections, and was built for Julia 0.7.
Version 1.8.0+ of OrderedCollections requires Julia 1.7.1, so chances are that anyone using a modern version of OrderedCollections will not be using the deprecated code blocks that have been removed in 2.0.0.

[bluesmoon]

I've also looked through the list of exports in DataStructures, and it does not appear that you export anything that was previously deprecated and now removed, so your API is still unchanged.