[inductor] fix test_dim_function_empty (#106994)
Summary: Looks like the assert syntax was just wrong
Test Plan:
PYTORCH_TEST_WITH_INDUCTOR=1 python test/test_torch.py -k test_dim_function_empty
PYTORCH_TEST_WITH_AOT_EAGER=1 python test/test_torch.py -k test_dim_function_empty
Pull Request resolved: https://github.com/pytorch/pytorch/pull/106994
Approved by: https://github.com/eellison
