bug: `getStaticDirectory()` removal breaks build

[Paul Phạm]

Describe the Bug

SvelteKit removed getStaticDirectory() function in sveltejs/kit#7809 breaks the build.

Steps to Reproduce

1. Build the project

Spits out errors:

> Using svelte-adapter-firebase
error during build:
TypeError: builder.getStaticDirectory is not a function
 at adapt (file:///./node_modules/.pnpm/file+..+svelte-adapter-firebase_u7k3ayrbkw2qngmchevq6cz5qu/node_modules/svelte-adapter-firebase/src/index.js:28:77)

Expected Behaviour

> Using svelte-adapter-firebase
  ✔ done

svelte-adapter-firebase version

0.14.4

sveltejs/kit version

1.0.0-next.570