suppress 'clippy::approx_constant' lint in test case

Author: danieleades

crates/syntax/src/ast/token_ext.rs

@@ -481,6 +481,7 @@ bcde", b"abcde",
 
     #[test]
     fn test_value_underscores() {
+        #[allow(clippy::approx_constant)]
         check_float_value("3.141592653589793_f64", 3.141592653589793_f64);
         check_float_value("1__0.__0__f32", 10.0);
         check_int_value("0b__1_0_", 2);