feat: drop get_device_warnings; the pending updates are the fact (0.3.0)

updates_available came from the cached firmware status with ten package
names; netOrk builds it from get_available_updates with the full list
(netOrk #1111).

tests/unit/test_updates.py

@@ -138,3 +138,11 @@ class TestRebootHost:
         with patch.object(driver, "_post", side_effect=ConnectionError("403 Forbidden")):
             with pytest.raises(RuntimeError, match="403"):
                 driver.reboot_host()
+
+
+def test_no_warnings_of_its_own():
+    """The pending updates are get_available_updates; the caller names
+    updates_available from them (netOrk #1111)."""
+    from napalm_opnsense.opnsense import OPNsenseDriver
+
+    assert "get_device_warnings" not in vars(OPNsenseDriver)