package.json: update rimraf

Minimum required Node.js version is 20 now.

Author: alanorth

package-lock.json

@@ -223,7 +223,7 @@
     "postcss-import": "^14.0.0",
     "postcss-loader": "^4.0.3",
     "postcss-preset-env": "^7.4.2",
-    "rimraf": "^3.0.2",
+    "rimraf": "^6.1.0",
     "sass": "~1.93.3",
     "sass-loader": "^12.6.0",
     "sass-resources-loader": "^2.2.5",