Revert "test: fix upgrade dhcp6 on ec2 (#5131)" (#5148)

This reverts commit 9758673.

Not needed after GH-5145.

tests/integration_tests/test_upgrade.py

@@ -153,13 +153,6 @@ def test_clean_boot_of_upgraded_package(session_cloud: IntegrationCloud):
             for values in post_network["network"]["ethernets"].values():
                 values.pop("dhcp6")
             assert yaml.dump(pre_network) == yaml.dump(post_network)
-        elif PLATFORM == "ec2":
-            # After GH-3980, EC2 does not enable dhcp6 anymore. This block can
-            # be removed after the base cloud-init version is 24.1.
-            pre_network = yaml.load(pre_network, Loader=yaml.Loader)
-            post_network = yaml.load(post_network, Loader=yaml.Loader)
-            pre_network["network"]["ethernets"]["ens5"]["dhcp6"] = False
-            assert yaml.dump(pre_network) == yaml.dump(post_network)
         else:
             assert pre_network == post_network