Fix: Move workspace modal token to workspace module

[madsrasmussen]

Description

From
import { UMB_WORKSPACE_MODAL } from '@umbraco-cms/backoffice/modal';

To
import { UMB_WORKSPACE_MODAL } from '@umbraco-cms/backoffice/workspace';

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (minor updates related to the tooling or maintenance of the repository, does not impact compiled assets)

[nielslyngsoe]

Looks good