chore: remove four modules nothing in the app uses (#1403)

* chore: remove four modules nothing in the app uses

src/app/sourceSlot.js re-exported src/sources/sourceSlot.js, which every
caller imports directly. src/data/flowTiles.js and src/data/issPass.js were
reached only by their own tests. src/data/localGeojson.js wrapped
localGeojsonCore.js with the app's services, which the catalog already
passes itself. The local GeoJSON layer tests now build layers the way the
catalog does, so they keep covering localGeojsonCore.js; only the test of
the wrapper's own default host goes. Boundary lists, format scope and docs
drop the removed paths.

* docs: changelog for #1403

src/layers/traffic/flowDecode.js

@@ -19,7 +19,7 @@ import { VectorTile } from '@mapbox/vector-tile';
  * tree-shakeable; decoding happens client-side so the proxy stays a dumb
  * binary cache.
  *
- * @module data/flowTiles
+ * @module layers/traffic/flowDecode
  */
 
 const FLOW_LAYER_NAME = 'Traffic flow';