Fix: Error data was JSON encoded twice

The result sent was always a string containing encoded JSON.

Solution: Use the argument `text` instead of `data` to pass the data as a UTF-8 string.

src/aleph/vm/orchestrator/views/__init__.py

@@ -350,7 +350,7 @@ async def update_allocations(request: web.Request):
         data = await request.json()
         allocation = Allocation.parse_obj(data)
     except ValidationError as error:
-        return web.json_response(data=error.json(), status=web.HTTPBadRequest.status_code)
+        return web.json_response(text=error.json(), status=web.HTTPBadRequest.status_code)
 
     pubsub: PubSub = request.app["pubsub"]
     pool: VmPool = request.app["vm_pool"]