[CHORE] Deprecate overture_releases.yaml

[lowlydba]

Motivation

Now that we have a mature implementation of STAC at https://stac.overturemaps.org, the overture_releases.yml doesn't provide any real benefits over the structured JSON alternative, except for being used to drive the latest.dbb generation (which will eventually be superseded by OvertureMaps/stac#67).

Once the stac includes the helper queries, we can remove both the util and yml file from here, redirecting folks to use the stac catalog instead.

[lowlydba]

Actually, while that is a great value-add metadata to have the STAC provide, we can make progress by just driving the latest.dbb generation using hosted STAC today.