[next][node][redwood][remix] Update @vercel/nft to 0.21.0 (#8208)

### Related Issues

Updates to the latest version of `@vercel/nft` which adds fs concurrency limits to help alleviate memory usage. 

x-ref: https://github.com/vercel/nft/pull/301

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#### Tests

- [ ] The code changed/added as part of this PR has been covered with tests
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test/lib/run-build-lambda.js

@@ -39,11 +39,13 @@ async function runBuildLambda(inputPath) {
     config: build.config,
   });
 
-  const workPath = path.join(
+  let workPath = path.join(
     os.tmpdir(),
     `vercel-${Date.now()}-${Math.floor(Math.random() * 100)}`
   );
   await fs.ensureDir(workPath);
+
+  workPath = await fs.realpath(workPath);
   console.log('building in', workPath);
 
   const buildResult = await wrapper.build({