Short answer
HubSpot's KB says workflows can remove association labels and, optionally, the associations that carry them, but it is not possible to remove associations without a label using workflows. For those, HubSpot recommends the API's remove association or delete multiple associations endpoints. It also recommends labeling associations so they can be managed in workflows later.
1. The workflow actions
Association actions in my demo portal's workflow picker.

2. By API
See associations v4 API.
3. Related
Labels and multiple companies.