Remove unused code warning

Author: ms2300

clippy_lints/src/methods.rs

@@ -1389,7 +1389,7 @@ fn lint_get_unwrap(cx: &LateContext<'_, '_>, expr: &hir::Expr, get_args: &[hir::
     // because they do not implement `IndexMut`
     let expr_ty = cx.tables.expr_ty(&get_args[0]);
     let get_args_str = snippet(cx, get_args[1].span, "_");
-    let mut needs_ref = false;
+    let needs_ref;
     let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
         needs_ref = get_args_str.parse::<usize>().is_ok();
         "slice"