Remove unnecessary walrus operator parentheses

[MichaReiser]

Our formatter currently always adds parentheses around the walrus (a := 5) operator in for/if/... cases

ruff/crates/ruff_python_formatter/src/expression/expr_named_expr.rs

Lines 32 to 41 in 3cda89e

	impl NeedsParentheses for ExprNamedExpr {
	fn needs_parentheses(
	&self,
	_parent: AnyNodeRef,
	_context: &PyFormatContext,
	) -> OptionalParentheses {
	// Unlike tuples, named expression parentheses are not part of the range even when
	// mandatory. See [PEP 572](https://peps.python.org/pep-0572/) for details.
	OptionalParentheses::Always
	}

The goal of this issue is to implement black's parentheses behavior (inside NeedsParentheses) and only preserve parentheses that are necessary.

https://github.com/psf/black/blob/b4dca26c7d93f930bbd5a7b552807370b60d4298/src/black/linegen.py#L1387-L1401

[zanieb]

Related discussion suggesting we may not want to always remove them(?) #4870

[MichaReiser]

Related discussion suggesting we may not want to always remove them(?) #4870

Oh thanks. Our formatter preserves parentheses for nested expression but removes them in if/for/... headers. I should have stated this more clearly