docs: fix usage string since clap 4
@@ -170,7 +170,7 @@ impl<'a, 'b> MDWriter<'a, 'b> {
.render_usage()
.to_string()
.lines()
- .skip(1)
+ .map(|l| l.strip_prefix("Usage:").unwrap_or(l))
.map(|l| l.trim())
.filter(|l| !l.is_empty())
.collect::<Vec<_>>()
