fix #6911 -- jupyter markdown source editor font size wrong

Author: williamstein

src/packages/frontend/jupyter/cell-input.tsx

@@ -293,6 +293,7 @@ export const CellInput: React.FC<CellInputProps> = React.memo(
       const cmOptions = options("markdown").toJS();
       return (
         <MarkdownInput
+          fontSize={props.font_size}
           enableMentions={true}
           cacheId={`${props.id}${frameActions.current?.frame_id}`}
           value={props.cell.get("input") ?? ""}