Eliminate workaround for pre-1.17 rustc in serde_derive

The oldest compiler supported by serde_derive by this point is 1.56.

serde_derive/src/try.rs

@@ -1,19 +1,16 @@
-use proc_macro2::{Punct, Spacing, TokenStream};
+use proc_macro2::TokenStream;
 use quote::quote;
 
 // None of our generated code requires the `From::from` error conversion
 // performed by the standard library's `try!` macro. With this simplified macro
 // we see a significant improvement in type checking and borrow checking time of
 // the generated code and a slight improvement in binary size.
 pub fn replacement() -> TokenStream {
-    // Cannot pass `$expr` to `quote!` prior to Rust 1.17.0 so interpolate it.
-    let dollar = Punct::new('$', Spacing::Alone);
-
     quote! {
         #[allow(unused_macros)]
         macro_rules! try {
-            (#dollar __expr:expr) => {
-                match #dollar __expr {
+            ($__expr:expr) => {
+                match $__expr {
                     _serde::__private::Ok(__val) => __val,
                     _serde::__private::Err(__err) => {
                         return _serde::__private::Err(__err);