CI: autofix rust code.

src/parser/footnote_reference.rs

@@ -115,7 +115,7 @@ fn inline_footnote<'r, 's>(
 
 #[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
 fn footnote_reference_only<'r, 's>(
-    context: Context<'r, 's>,
+    _context: Context<'r, 's>,
     input: OrgSource<'s>,
 ) -> Res<OrgSource<'s>, FootnoteReference<'s>> {
     let (remaining, _) = tag_no_case("[fn:")(input)?;