Re-enable the max-len ESLint rule. (#5265)

packages/babel-core/src/transformation/plugin.js

@@ -1,5 +1,3 @@
-/* eslint max-len: 0 */
-
 import OptionManager from "./file/options/option-manager";
 import * as messages from "babel-messages";
 import Store from "../store";
@@ -85,7 +83,8 @@ export default class Plugin extends Store {
   normaliseVisitor(visitor: Object): Object {
     for (const key of GLOBAL_VISITOR_PROPS) {
       if (visitor[key]) {
-        throw new Error("Plugins aren't allowed to specify catch-all enter/exit handlers. Please target individual nodes.");
+        throw new Error("Plugins aren't allowed to specify catch-all enter/exit handlers. " +
+          "Please target individual nodes.");
       }
     }