Replace deprecated django.utils.datetime_safe

datetime_safe was deprecated and was removed in Django 5.0 [1].

[1] https://code.djangoproject.com/ticket/32738

Story: 2011506
Task: 52652
Change-Id: Icf7c07bc5b8c6f974980b1ecaba843d0bf599961
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>

heat_dashboard/test/test_data/keystone_data.py

@@ -13,10 +13,9 @@
 #    under the License.
 
 import copy
-from datetime import timedelta
+import datetime
 
 from django.conf import settings
-from django.utils import datetime_safe
 
 from keystoneclient import access
 from keystoneclient.v2_0 import tenants
@@ -235,7 +234,7 @@ def data(TEST):
     TEST.tenants.add(tenant, disabled_tenant, tenant_unicode)
     TEST.tenant = tenant  # Your "current" tenant
 
-    tomorrow = datetime_safe.datetime.now() + timedelta(days=1)
+    tomorrow = datetime.datetime.now() + datetime.timedelta(days=1)
     expiration = tomorrow.isoformat()
 
     scoped_token_dict = {