test: count News beside Wildlife Sightings

The catalog holds 39 layers, News ends the Events group just before
Wildlife, and the README names twenty-three layers.

src/app/sourceComposition.test.mjs

@@ -37,7 +37,7 @@ test('every acquisition source can be omitted without losing catalog membership'
 
 test('all acquisition sources may be absent, and enable fails before initializing or fetching', async (t) => {
   const actual = catalog({}, t);
-  assert.equal(actual.layers.length, 38);
+  assert.equal(actual.layers.length, 39);
   const manager = new LayerLifecycle(
     {},
     { getSourceAvailability: actual.getSourceAvailability },