README dependency table lists stale SDK versions

The README's **Key Dependencies** table is out of sync with the versions that the template actually installs.

In `package.json`, the SDK packages are pinned to `0.15.3`:

```json
"@miden-sdk/miden-sdk": "0.15.3",
"@miden-sdk/react": "0.15.3",
"@miden-sdk/vite-plugin": "0.15.3"
```

But the README table still lists those three rows as `0.15.2`.

This can confuse users checking the template docs before installing or comparing the template against the current SDK release. The fix should be small: update the README table so the documented pins match `package.json`.