Use macOS M1 runner in generated GitHub Actions configuration

[messense]

No need to cross compiling to macOS arm64 on x86_64 now that GitHub Actions has macOS M1 runners (macos-14).

maturin/src/ci.rs

Lines 213 to 222 in b209c4b

	let plat_name = platform.to_string();
	let os_name = match platform {
	Platform::Linux | Platform::Emscripten => "ubuntu",
	_ => &plat_name,
	};
	needs.push(platform.to_string());
	conf.push_str(&format!(
	" {plat_name}:
	runs-on: {os_name}-latest\n"
	));