Remove redundant prefresh dependency in with-preact example (vercel#23567)

The package `next-plugin-preact` [already contains](https://github.com/preactjs/next-plugin-preact/blob/38cfb182ddd4720ac5f8ea885929e4c1423cc267/packages/next-plugin-preact/package.json#L25) the dependency `@prefresh/next` so it shouldn't be explicitly installed.

## Documentation / Examples

- [x] Make sure the linting passes

Author: zephraph

examples/using-preact/package.json

@@ -8,7 +8,6 @@
   },
   "devDependencies": {},
   "dependencies": {
-    "@prefresh/next": "^1.3.0",
     "next": "^10.0.0",
     "next-plugin-preact": "^3.0.3",
     "preact": "^10.5.5",