Revert Data Join example until feature.id type issues are resolved

[asheemmamoowala]

#6580 updated the Data Join example to use the new Map#setFeatureState API. While the updated example shows the power of using the new API for data joins, it causes confusion with developers trying to use it in two ways:

1. Input features must have numeric ids assigned. Non numeric/string ids (valid in GeoJSON) are not supported and break silently. ref: query*Features should preserve non-integer feature IDs #2716, Map#setFeatureState should reject feature identifier without an id field #6959
2. Mapbox's own APIs sometimes discard the feature ids in input data when creating a Tileset.

cc @ryanbaumann @samgehret

[andrewharvey]

2. Mapbox's own APIs sometimes discard the feature ids in input data when creating a Tileset.

ref #6019 (comment) but I wouldn't hold off the data join examples because of this.

[asheemmamoowala]

@andrewharvey we have discovered a few other ways that the ids are re-created or dropped. Overall the demo creates more trouble for developers with data outside of their control. It should be back soon as a few PR fixes land.

A couple PRs related to this:

• Assign the cluster id to the returned GeoJSON Feature.id property supercluster#94
• Åuto-generation and promotion options for Feature Ids geojson-vt#109

[ryanhamley]

Looks good!