chore(nextjs): Add incremental option to nextjs integration test tsconfig (#4248)

Recently[1], nextjs started auto-defaulting the `incremental` tsconfig option[2] (which caches certain information build to build) to `true` in nextjs projects using typescript, by modifying the projects' `tsconfig` files.

This incorporates that `tsconfig` change into the app we use for integration tests.

[1] vercel/next.js#29169
[2] https://www.typescriptlang.org/tsconfig#incremental

Author: lobsterkatie

packages/nextjs/test/integration/tsconfig.json

@@ -16,7 +16,8 @@
     "resolveJsonModule": true,
     "skipLibCheck": true,
     "strict": true,
-    "target": "esnext"
+    "target": "esnext",
+    "incremental": true
   },
   "exclude": ["node_modules"],
   "include": ["**/*.ts", "**/*.tsx"]