instrumentation/django: fix test_trace_parent

Remove async keyword that did not make the test run and then fix tests
to send the traceparent as header instead of query string.

Fix open-telemetry#2236

Author: xrmx

Diff for: instrumentation/opentelemetry-instrumentation-django/tests/test_middleware.py

@@ -390,15 +390,15 @@ def response_hook(span, request, response):
         self.assertIsInstance(response_hook_args[2], HttpResponse)
         self.assertEqual(response_hook_args[2], response)
 
-    async def test_trace_parent(self):
+    def test_trace_parent(self):
         id_generator = RandomIdGenerator()
         trace_id = format_trace_id(id_generator.generate_trace_id())
         span_id = format_span_id(id_generator.generate_span_id())
         traceparent_value = f"00-{trace_id}-{span_id}-01"
 
         Client().get(
             "/span_name/1234/",
-            traceparent=traceparent_value,
+            headers={"traceparent": traceparent_value},
         )
         span = self.memory_exporter.get_finished_spans()[0]