Chore: type the set-permissions dict

Callers passed whatever they had, including querysets of User and Group
objects that only worked because id__in accepts a subquery.

src/documents/workflows/mutations.py

@@ -7,6 +7,7 @@ from documents.data_models import DocumentMetadataOverrides
 from documents.models import CustomFieldInstance
 from documents.models import Document
 from documents.models import WorkflowAction
+from documents.permissions import PermissionsSpec
 from documents.permissions import set_permissions_for_objects
 from documents.templating.workflows import parse_w_workflow_placeholders
 
@@ -73,7 +74,7 @@ def apply_assignment_to_document(
             action.has_assign_change_groups,
         ],
     ):
-        permissions = {
+        permissions: PermissionsSpec = {
             "view": {
                 "users": action.assign_view_users.values_list("id", flat=True),
                 "groups": action.assign_view_groups.values_list("id", flat=True),
@@ -244,7 +245,7 @@ def apply_removal_to_document(
         document.owner = None
 
     if action.remove_all_permissions:
-        permissions = {
+        permissions: PermissionsSpec = {
             "view": {"users": [], "groups": []},
             "change": {"users": [], "groups": []},
         }