Fix E731: Convert lambda assignments to def functions

[Copilot]

Reduces ignored ruff rules by fixing all E731 violations ("do not assign a lambda expression, use a def").

Changes

• apex/contrib/openfold_triton/layer_norm.py: Convert 3 grid lambda assignments to def functions
• apex/contrib/openfold_triton/mha.py: Convert 2 grid lambda assignments to def functions
• examples/imagenet/main_amp.py: Convert collate_fn lambda to def function
• pyproject.toml: Remove E731 from ignore list

Example

# Before
grid = lambda kwargs: (triton.cdiv(kwargs["M"], kwargs["M_BLOCK"]),)

# After
def grid(kwargs):
    return (triton.cdiv(kwargs["M"], kwargs["M_BLOCK"]),)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Reduce the number of ignored rules</issue_title>
<issue_description>Create a pull request per ignored rule listed in

apex/pyproject.toml

Lines 8 to 25 in 87868b0

	[tool.ruff]
	line-length = 100
	ignore = [
	# Sorted by occurrence count (ascending) - easier to fix first
	"E731", # lambda assignment (6 occurrences)
	"E721", # type comparison should use isinstance (8 occurrences)
	"E741", # ambiguous variable name (8 occurrences)
	"E712", # comparison to True/False (9 occurrences)
	"F403", # star imports used (9 occurrences)
	"E701", # multiple statements on one line (10 occurrences)
	"E711", # comparison to None should be `cond is None` (11 occurrences)
	"F821", # undefined name (14 occurrences)
	"E722", # bare except (15 occurrences)
	"E402", # module level import not at top of file (41 occurrences)
	"F401", # imported but unused (45 occurrences)
	"F841", # local variable assigned but never used (52 occurrences)
	"F405", # star imports (80 occurrences)
	]

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Reduce the number of ignored rules #1964

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