Remove the explicit role for ACE

[vhvb1989]

Remove the explicitContributorUserRoleAssignment from the resources/apphost/templates/resources.bicept
We needed this role to workaround an issue with the Aspire Dashboard, but it is not required anymore.

After updating this file, we need to re-run and re-create the snapshots for pkg/apphost/generate_test.go to work.