test: move the tzdb version test into tests/ so npm test runs it

tests/timezones/tzdb.test.js

@@ -0,0 +1,9 @@
+import test from 'tape'
+import spacetime from '../_lib/index.js'
+import { tzdbVersion } from '../../zonefile/iana.js'
+
+test('tzdb version', (t) => {
+  t.ok(/^\d{4}[a-z]+$/.test(spacetime.tzdbVersion), `looks like '2026c'`)
+  t.equal(spacetime.tzdbVersion, tzdbVersion, 'same as zonefile/iana.js')
+  t.end()
+})