[Tracking] Improve Android API compat test in POM

Currently in the POM we have this:

https://github.com/jhy/jsoup/blob/19c758e2e4abc6a1f52193ceab09c22a7c010f8b/pom.xml#L115-L155

Because the Maven Animal Sniffer plugin doesn't currently support a classifier (https://github.com/mojohaus/animal-sniffer/issues/328), we can't specify the Gummy Bears API definition for coreLib2. So I've been updating the POM with manual exclusions. But that's dull and a bit risky.

So I've added a PR to implement the classifier support: https://github.com/mojohaus/animal-sniffer/pull/346

Assuming that lands we should be able to simplify this POM quite a bit.

It will be good also if Gummy Bears has a coreLib2 + NIO definition set, because that's what jsoup aligns to.