Fix indentation in test assertion

Corrected the indentation of the assertion checking the exit code in
`tests/test_run.py`. This ensures the test correctly validates the exception
code raised.

tests/test_run.py

@@ -2878,7 +2878,7 @@ def test_unknown_system(self, caplog, monkeypatch):
                 cpu_arch="",
             )
 
-            assert exc.value.code == 2
+        assert exc.value.code == 2
         assert caplog.records[0].levelname == "ERROR"
         assert caplog.records[0].message == "unknown system: mythical"