[BUG] Creating new project in empty directory fails

### Describe the bug

Running `npx projen new --from @aws/pdk --package-manager=pnpm monorepo-ts` on empty new folder creates following error
```
C:\Users\{username}\{project_folder}\node_modules\projen\lib\file.js:98
throw new Error(`There is already a file under ${rootProjectPath}`);
Error: There is already a file under pnpm-workspace.yaml
```

### Expected Behavior

Should generate new project without error

### Current Behavior

Failes with the above error

### Reproduction Steps

Running `npx projen new --from @aws/pdk --package-manager=pnpm monorepo-ts` in empty folder should reproduce it

### Possible Solution

_No response_

### Additional Information/Context

_No response_

### PDK version used

latest version downloaded automatically trough npx

### What languages are you seeing this issue on?

_No response_

### Environment details (OS name and version, etc.)

Windows 11

Reproduce the issue with `npx projen new --from @aws/pdk --package-manager=pnpm monorepo-ts` in an empty Windows directory. Start at `node_modules/projen/lib/file.js` around line 98 and trace why `pnpm-workspace.yaml` is treated as an existing file; done means the command completes and generates the project without the error.

Written by the indexing model from the issue text.