[Security Solution] Fix data generator so that it will load dev endpoint packages (#147149)

## Summary

Fixes the generator script by including the `prerelease` flag in the
install package call.

<img width="1552" alt="image"
src="https://user-images.githubusercontent.com/56395104/206051967-b9356243-58cb-4a12-8457-247cc5f44e8e.png">

<img width="1726" alt="image"
src="https://user-images.githubusercontent.com/56395104/206052008-ca0f341c-8a33-4655-be62-218e5b7515fd.png">

### Checklist
- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>

x-pack/plugins/security_solution/common/endpoint/data_loaders/setup_fleet_for_endpoint.ts

@@ -95,6 +95,9 @@ export const installOrUpgradeEndpointFleetPackage = async (
       body: {
         packages: ['endpoint'],
       },
+      query: {
+        prerelease: true,
+      },
     })
     .catch(wrapErrorAndRejectPromise)) as AxiosResponse<BulkInstallPackagesResponse>;