Update label extension to `1.0.1`

[cuttlefish]

The Label extension has been updated. I tried changing the version number here but the tests failed. I haven't had time to look into it yet.

[duckontheweb]

It looks like jsonschema is not able to resolve the "#/definitions/link_fields" reference in the updated schema. I don't see anything wrong with the schema itself, so I'm wondering if it has to do with the way we are creating and caching the RefResolver that gets passed in here.

I'll try to dig into this a bit more, but I probably won't have a chance until at least later tonight or tomorrow since I'm not as familiar with the validation code.

[duckontheweb]

@cuttlefish Finally had a chance to look into this some more and it turns out the JSON schema for the Label Extension v1.0.1 release was incorrect (it was still checking for the v1.0.0 schema URI in stac_extensions). I opened stac-extensions/label#9 and will re-publish that release once things have been merged.