Remove note about their being more parts to the tutorial

We'll ship more stuff when we do. No reason to make it sound less than useful as it is.

www/src/pages/tutorial.js

@@ -11,8 +11,8 @@ export default () => (
     </Helmet>
     <h1 css={{ marginTop: 0 }}>Gatsby.js Tutorial</h1>
     <p>
-      Hi! We’re so happy you decided to try using Gatsby. This tutorial has (or
-      rather will have once all parts are written) five parts that'll walk you
+      Hi! We’re so happy you decided to try using Gatsby. This tutorial has five
+  parts that'll walk you
       from getting started developing and building Gatsby sites to deploying a
       finished and polished high performance static PWA.
     </p>