chore(django-spanner): stabilize Django 5.2 system tests and remove obsolete workflows

Author: sinhasubham

.github/workflows/django-spanner-integration-tests-against-emulator-3.8.yml

@@ -132,7 +132,7 @@ def instance(self):
 
         if _SPANNER_CLIENT_CACHE is None:
             _SPANNER_CLIENT_CACHE = spanner.Client(
-                project=os.environ["GOOGLE_CLOUD_PROJECT"]
+                project=os.environ.get("GOOGLE_CLOUD_PROJECT") or self.settings_dict.get("project") or self.settings_dict.get("PROJECT") or "test-project"
             )
 
         return _SPANNER_CLIENT_CACHE.instance(self.settings_dict["INSTANCE"])
@@ -155,7 +155,7 @@ def get_connection_params(self):
                   in Django Spanner format.
         """
         return {
-            "project": os.environ["GOOGLE_CLOUD_PROJECT"],
+            "project": os.environ.get("GOOGLE_CLOUD_PROJECT") or self.settings_dict.get("project") or self.settings_dict.get("PROJECT") or "test-project",
             "instance_id": self.settings_dict["INSTANCE"],
             "database_id": self.settings_dict["NAME"],
             "user_agent": "django_spanner/2.2.0a1",