style: set black line-length=120 and reformat test_moe.py

Uncomment line-length = 120 in [tool.black] (it was already written
but commented out).  With 120-char lines the parameterized test-case
tables in test_moe.py fit on a single line each, reducing the file
from 1445 lines (88-char limit) back to 895 lines.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: yizhuoz004

pyproject.toml

@@ -363,7 +363,7 @@ py_version = 311
 skip = ["py/torch_tensorrt/fx"]
 
 [tool.black]
-#line-length = 120
+line-length = 120
 target-version = ["py38", "py39", "py310", "py311", "py312"]
 force-exclude = """
 elu_converter/setup.py