Update RefContext to three lifetimes.

src/parser/horizontal_rule.rs

@@ -15,7 +15,7 @@ use crate::parser::HorizontalRule;
 
 #[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
 pub fn horizontal_rule<'r, 's>(
-    _context: RefContext<'r, 's>,
+    _context: RefContext<'_, 'r, 's>,
     input: OrgSource<'s>,
 ) -> Res<OrgSource<'s>, HorizontalRule<'s>> {
     start_of_line(input)?;