fix flux unittest

Author: wwwjn

.github/workflows/flux_unit_test_cpu.yaml

@@ -30,4 +30,4 @@ jobs:
         pip config --user set global.progress_bar off
 
         pip install --force-reinstall --pre torch --index-url https://download.pytorch.org/whl/nightly/cpu
-        pytest experiments/flux/tests/unit_tests/ --cov=. --cov-report=xml --durations=20 -vv
+        pytest torchtitan/experiments/flux/tests/unit_tests/ --cov=. --cov-report=xml --durations=20 -vv