Address review comments

Author: lukaslueg

clippy_lints/src/size_of_ref.rs

@@ -66,7 +66,7 @@ impl LateLintPass<'_> for SizeOfRef {
                 expr.span,
                 "argument to `std::mem::size_of_val()` is a reference to a reference",
                 None,
-                "dereference the argument to `std::mem::size_of_val()` to get the size of the value instead of the generic size of any reference-type",
+                "dereference the argument to `std::mem::size_of_val()` to get the size of the value instead of the size of the reference-type",
             );
         }
     }