Add missing symbols (#2883)

Signed-off-by: cuishuang <imcusg@gmail.com>

Author: cuishuang

futures-macro/src/join.rs

@@ -1,4 +1,4 @@
-//! The futures-rs `join! macro implementation.
+//! The futures-rs `join!` macro implementation.
 
 use proc_macro::TokenStream;
 use proc_macro2::{Span, TokenStream as TokenStream2};

futures-macro/src/select.rs

@@ -1,4 +1,4 @@
-//! The futures-rs `select! macro implementation.
+//! The futures-rs `select!` macro implementation.
 
 use proc_macro::TokenStream;
 use proc_macro2::Span;