Solve the rest of the compiler warnings.

src/parser/element_parser.rs

@@ -12,8 +12,6 @@ use super::lesser_block::verse_block;
 use super::paragraph::paragraph;
 use super::plain_list::plain_list;
 use super::Context;
-use crate::error::CustomError;
-use crate::error::MyError;
 use crate::error::Res;
 use crate::parser::parser_with_context::parser_with_context;
 use crate::parser::table::org_mode_table;