Auto merge of #8433 - giraffate:update_built-in_help_for_features, r=alexcrichton

Update built-in help for features

Fixed #8381.

Author: bors

src/cargo/util/command_prelude.rs

@@ -117,7 +117,7 @@ pub trait AppExt: Sized {
         self._arg(multi_opt(
             "features",
             "FEATURES",
-            "Space-separated list of features to activate",
+            "Space or comma separated list of features to activate",
         ))
         ._arg(opt("all-features", "Activate all available features"))
         ._arg(opt(