Remove `#[cfg(proc_macro_span)]` from span-locations

[nurmohammed840]

Hello,

Currently, the implementation of Span::start() (and related functions) under the span-locations feature is guarded
by #[cfg(proc_macro_span)].

proc-macro2/src/wrapper.rs

Lines 431 to 443 in fc2ae0f

	#[cfg(span_locations)]
	pub(crate) fn start(&self) -> LineColumn {
	match self {
	#[cfg(proc_macro_span)]
	Span::Compiler(s) => LineColumn {
	line: s.line(),
	column: s.column().saturating_sub(1),
	},
	#[cfg(not(proc_macro_span))]
	Span::Compiler(_) => LineColumn { line: 0, column: 0 },
	Span::Fallback(s) => s.start(),
	}
	}

This condition bypass span information (such as line and column numbers).

However those function are stabilized in Version 1.88.0

Proposal: Remove #[cfg(proc_macro_span)] attribute

[nurmohammed840]

If you're currently busy, I’d be happy to submit a pull request