[WIP] npm: set engines to Node ^20.15.0 and npm ^10.7.0

Actually required for the "simplesettings" app. Since the workflow
initially "sees" the Nextcloud package.json.

Since entering each app directory and setting up different Node/npm
versions is no feasible anyway, let's set it here.

package.json

@@ -194,8 +194,8 @@
     "extends @nextcloud/browserslist-config"
   ],
   "engines": {
-    "node": "^20.0.0",
-    "npm": "^10.0.0"
+    "node": "^20.15.0",
+    "npm": "^10.7.0"
   },
   "overrides": {
     "colors": "1.4.0"