Remove TODO.

I tested and we cannot nest different types of dynamic blocks.

src/parser/dynamic_block.rs

@@ -40,7 +40,6 @@ pub(crate) fn dynamic_block<'b, 'g, 'r, 's>(
     context: RefContext<'b, 'g, 'r, 's>,
     input: OrgSource<'s>,
 ) -> Res<OrgSource<'s>, DynamicBlock<'s>> {
-    // TODO: Do I need to differentiate between different dynamic block types.
     if immediate_in_section(context, "dynamic block") {
         return Err(nom::Err::Error(CustomError::MyError(MyError(
             "Cannot nest objects of the same element".into(),