refactor: remove specification of operators for ternary operator

I don't plan on adding other ternary operators. So we just gonna assume
that we only have one ternary operator, which is ? !

src/ast.rs

@@ -4,9 +4,7 @@ use crate::token::{LiteralType, Token};
 pub enum Expr {
     Ternary {
         first: Box<Expr>,
-        first_op: Token,
         second: Box<Expr>,
-        second_op: Token,
         third: Box<Expr>,
     },
     Binary {

src/parser.rs

@@ -50,15 +50,12 @@ impl Parser<'_> {
         let expr = self.equality()?;
 
         if self.match_token(&[Question]) {
-            let first_op = self.previous().clone();
             let second = self.expression()?;
-            let second_op = self.consume(Colon, "Expected : after ternary operator ?")?;
+            let _ = self.consume(Colon, "Expected : after ternary operator ?")?;
             let third = self.ternary()?;
             return Ok(Expr::Ternary {
                 first: Box::new(expr),
-                first_op,
                 second: Box::new(second),
-                second_op,
                 third: Box::new(third),
             });
         }

src/printer.rs

@@ -13,14 +13,9 @@ pub fn pretty_print(expr: &Expr) -> String {
         Expr::Unary { op, right } => parenthesize(&op.lexeme, &[right]),
         Expr::Ternary {
             first,
-            first_op,
             second,
-            second_op,
             third,
-        } => parenthesize(
-            &format!("{}{}", first_op.lexeme, second_op.lexeme),
-            &[first, second, third],
-        ),
+        } => parenthesize("?:", &[first, second, third]),
     }
 }