remove redundant unknown transformer error message

lib/babel/transformation/index.js

@@ -41,12 +41,7 @@ transform._ensureTransformerNames = function (type, rawKeys) {
       keys = keys.concat(transform.namespaces[key]);
     } else {
       // invalid key
-      throw new ReferenceError(
-        "Unknown transformer " + key + " specified in " + type + " - " +
-        "transformer key names have been changed in 3.0.0 see " +
-        "the changelog for more info " +
-        "https://github.com/babel/babel/blob/master/CHANGELOG.md#300"
-      );
+      throw new ReferenceError("Unknown transformer " + key + " specified in " + type);
     }
   }