fix line

Author: nikomatsakis

src/test/ui/issue-29723.rs

@@ -20,7 +20,7 @@ fn main() {
             // This should trigger an error,
             // s could have been moved from.
             s
-            //~ ERROR use of moved value: `s`
+            //~^ ERROR use of moved value: `s`
         }
     };
 }