Fix paths to vagrant configs in both playground and sandbox repos (#244)

## Description

Fix paths to vagrant configs in both playground and sandbox repos

## Why is this needed

To fix minor bugs while following https://tinkerbell.org/docs/setup/getting_started

Fixes: #

## How Has This Been Tested?





## How are existing users impacted? What migration steps/scripts do we need?





## Checklist:

I have:

- [x] updated the documentation and/or roadmap (if required)
- [ ] added unit or e2e tests
- [ ] provided instructions on how to upgrade

content/docs/setup/getting_started.md

@@ -35,7 +35,7 @@ Follow these steps to create the stack on a Libvirt VM using Vagrant. Then deplo
 1. Start the stack
 
    ```bash
-   cd vagrant
+   cd stack/vagrant
    vagrant up
    # This process will take about 5-10 minutes depending on your internet connection.
    # Hook is about 400MB in size and the Ubuntu jammy image is about 500MB
@@ -513,7 +513,7 @@ Follow these steps to create the stack on a Virtualbox VM using Vagrant. Then de
 1. Start the stack
 
    ```bash
-   cd vagrant
+   cd stack/vagrant
    vagrant up
    # This process will take up to 10 minutes depending on your internet connection.
    # It will download HookOS, which is a couple hundred megabytes in size, and an Ubuntu cloud image, which is about 600MB.
@@ -976,4 +976,4 @@ Need a little help getting started? We're here!
 [faqs]: /faq/
 [github]: https://github.com/tinkerbell
 [#tinkerbell]: https://app.slack.com/client/T08PSQ7BQ/C01SRB41GMT
-[playground]: https://github.com/tinkerbell/playground
+[playground]: https://github.com/tinkerbell/playground