fix(nx-cloud): add nxCloudId to nxJson when connecting with generator (#27356)

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## Current Behavior
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When connecting via NxCloudId, the resulting Id would not be written to
nx.json

## Expected Behavior
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Correctly writes nxCloudId to nx.json after running `npx nx g
connect-to-nx-cloud`

## Related Issue(s)
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merged. -->

Fixes #

packages/nx/src/nx-cloud/generators/connect-to-nx-cloud/connect-to-nx-cloud.ts

@@ -150,7 +150,7 @@ function addNxCloudOptionsToNxJson(
 function addNxCloudIdToNxJson(
   tree: Tree,
   nxCloudId: string,
-  directory: string = tree.root
+  directory: string = ''
 ) {
   const nxJsonPath = join(directory, 'nx.json');
   if (tree.exists(nxJsonPath)) {