Platform.sh custom xdebug configuration example not working

**Link to the page that needs to be updated or changed.**
https://docs.lando.dev/config/platformsh.html#xdebug

**Describe the change you'd like**
The example custom xdebug configuration is not picked up by lando.

```
config:
id: PROJECT_ID
overrides:
app:
runtime:
extensions:
- redis
- xdebug
php:
# XDEBUG 2
xdebug.remote_enable: 1
xdebug.remote_mode: req
xdebug.remote_port: 9000
xdebug.remote_connect_back: 0
```

After placing the configuration in many different places, the following location was discovered to work correctly.
```
name: PROJECT_ID
config:
variables:
app:
php:
xdebug.remote_enable: 1
xdebug.remote_mode: req
xdebug.remote_port: 9000
xdebug.remote_connect_back: 0
overrides:
app:
runtime:
extensions:
- redis
- xdebug
```

Open the Xdebug section at https://docs.lando.dev/config/platformsh.html#xdebug and compare its example with the working configuration shown in the issue. Update the documented configuration so the custom Xdebug settings are placed where Platform.sh picks them up, then verify the example remains valid YAML and renders correctly in the documentation.

Written by the indexing model from the issue text.