We recently started validating the `Pulumi.yaml` file against its schema, leading to the following error when the `refresh: always` option is specified:
```
error: could not load current project: 1 error occurred:
* #/options/refresh: expected boolean, but got string
```
The problem is the feature is expecting a string value of `"always"` but the schema for the project file is incorrectly specified as `boolean`.
This change fixes the schema, which avoids the error. A separate change will fix the documentation at https://www.pulumi.com/docs/reference/pulumi-yaml/#options-options