chore(integ): correct --silent flag in yarn workspaces info (#15175)

## Overview

The `--silent` flag in `yarn workspaces info` does not works.
The `--json` flag is suggested in yarnpkg/yarn#7881.

The output of `yarn workspaces --json info` is as follows and requires `JSON.parse()` twice:

```
{"type":"log","data":"{\n  \"aws-cdk-lib\": {\n    \"location\" --- snip --- \"workspaceDependencies\": [],\n    \"mismatchedWorkspaceDependencies\": []\n  }\n}"}
```

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/aws-cdk/test/integ/helpers/monorepo.ts

@@ -13,7 +13,7 @@ const YARN_MONOREPO_CACHE: Record<string, any> = {};
  */
 export async function findYarnPackages(root: string): Promise<Record<string, string>> {
   if (!(root in YARN_MONOREPO_CACHE)) {
-    const output: YarnWorkspacesOutput = JSON.parse(await shell(['yarn', 'workspaces', 'info', '--silent'], {
+    const output: YarnWorkspacesOutput = JSON.parse(await shell(['yarn', 'workspaces', '--silent', 'info'], {
       captureStderr: false,
       cwd: root,
     }));