Minor documentation fix for race and try_race (#473)

Author: abhishekc-sharma

src/future/future/mod.rs

@@ -187,11 +187,9 @@ extension_trait! {
             futures to complete. If multiple futures are completed at the same time,
             resolution will occur in the order that they have been passed.
 
-            Note that this macro consumes all futures passed, and once a future is
+            Note that this function consumes all futures passed, and once a future is
             completed, all other futures are dropped.
 
-            This macro is only usable inside of async functions, closures, and blocks.
-
             # Examples
 
             ```