fix(lint): remove trailing whitespace from blank lines in test files

backend/tests/test_techniques.py

@@ -53,7 +53,7 @@ def test_create_duplicate_technique(client, auth_headers):
         json={"mitre_id": "T1001", "name": "First"},
         headers=auth_headers,
     )
-    
+
     # Try to create duplicate
     response = client.post(
         "/api/v1/techniques",
@@ -71,7 +71,7 @@ def test_get_technique_by_mitre_id(client, auth_headers):
         json={"mitre_id": "T1059", "name": "Test Technique"},
         headers=auth_headers,
     )
-    
+
     # Get it by mitre_id
     response = client.get("/api/v1/techniques/T1059", headers=auth_headers)
     assert response.status_code == 200
@@ -92,7 +92,7 @@ def test_update_technique(client, auth_headers):
         json={"mitre_id": "T1059", "name": "Original Name"},
         headers=auth_headers,
     )
-    
+
     # Update it
     response = client.patch(
         "/api/v1/techniques/T1059",
@@ -116,7 +116,7 @@ def test_filter_techniques_by_tactic(client, auth_headers):
         json={"mitre_id": "T1002", "name": "Persist", "tactic": "persistence"},
         headers=auth_headers,
     )
-    
+
     # Filter by execution
     response = client.get(
         "/api/v1/techniques?tactic=execution",