Remove unused import

Part of rustwasm#670

Author: kraai

crates/js-sys/tests/wasm/Symbol.rs

@@ -1,6 +1,5 @@
 use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
-use wasm_bindgen::JsCast;
 use js_sys::*;
 
 #[wasm_bindgen(module = "tests/wasm/Symbol.js")]