refactor: replace Jest with bun

.github/workflows/ci-checks.yml

@@ -15,11 +15,6 @@ jobs:
         with:
           bun-version: 1.3.14
 
-      # Jest still runs on Node until tests move to `bun test`
-      - uses: actions/setup-node@v3
-        with:
-          node-version: 20
-
       - name: Install dependencies
         run: bun install --frozen-lockfile