tweak lock message

Change the message from
waiting for file lock on package cache lock
to
waiting for file lock on package cache

src/cargo/util/config.rs

@@ -882,7 +882,7 @@ impl Config {
             }
             None => {
                 let path = ".package-cache";
-                let desc = "package cache lock";
+                let desc = "package cache";
 
                 // First, attempt to open an exclusive lock which is in general
                 // the purpose of this lock!