Release patch version of Reffy - v15.2.1

Patches:
- Stop fetching resources from test.csswg.org (#1579)

Dependencies bumped:
- Bump ajv from 8.14.0 to 8.15.0 (#1578)
- Bump web-specs from 3.8.0 to 3.9.1 (#1559, #1577)
- Bump semver from 7.6.0 to 7.6.2 (#1564)
- Bump ajv from 8.12.0 to 8.14.0 (#1575)
- Bump undici from 6.13.0 to 6.18.2 (#1576)
- Bump respec from 34.5.0 to 35.0.2 (#1556)
- Bump puppeteer from 22.6.5 to 22.10.0 (#1574)
- Bump rollup from 4.14.3 to 4.18.0 (#1572)
- Bump commander from 12.0.0 to 12.1.0 (#1570)

Author: tidoust

package.json

@@ -1,6 +1,6 @@
 {
   "name": "reffy",
-  "version": "15.2.0",
+  "version": "15.2.1",
   "description": "W3C/WHATWG spec dependencies exploration companion. Features a short set of tools to study spec references as well as WebIDL term definitions and references found in W3C specifications.",
   "repository": {
     "type": "git",