Use preferred header syntax

Author: gone

debug_toolbar/middleware.py

@@ -132,6 +132,6 @@ def generate_headers(request, response, panels):
                 )
 
         if stats_data:
-            response["Server-Timing"] = ", ".join(stats_data)
+            response.headers["Server-Timing"] = ", ".join(stats_data)
 
         return response

debug_toolbar/panels/history/panel.py

@@ -25,7 +25,7 @@ def generate_headers(self, request, response):
         observe_request = get_observe_request()
         store_id = getattr(self.toolbar, "store_id")
         if store_id and observe_request(request):
-            response["DJDT-STORE-ID"] = store_id
+            response.headers["DJDT-STORE-ID"] = store_id
         return response
 
     @property