build: use latest node on travis

PR-URL: https://github.com/nodejs/node/pull/24198
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>

.travis.yml

@@ -5,7 +5,8 @@ os: linux
 matrix:
   include:
     - name: "Linter"
-      node_js: "latest"
+      language: node_js
+      node_js: "node"
       env:
         - NODE=$(which node)
       script: