Fix geoapi store geojson for live layers

src/gisaf/geoapi.py

@@ -64,7 +64,8 @@ async def get_geojson(store_name,
     if await redis_store.has_channel(store_name):
         ## Live layers
         data = await redis_store.get_layer_as_json(store_name)
-        return data.decode()
+        return Response(content=data.decode(),
+                        media_type="application/json")
 
     # elif not model:
     #     raise HTTPException(status.HTTP_404_NOT_FOUND)