Begin removing the MyError type.

src/parser/latex_fragment.rs

@@ -17,7 +17,6 @@ use super::util::maybe_consume_object_trailing_whitespace_if_not_exiting;
 use crate::context::parser_with_context;
 use crate::context::RefContext;
 use crate::error::CustomError;
-use crate::error::MyError;
 use crate::error::Res;
 use crate::parser::util::exit_matcher_parser;
 use crate::parser::util::get_consumed;