Remove dot from the end of the link (facebook#5449)

Author: ranyitz

packages/react-scripts/template/src/serviceWorker.js

@@ -8,7 +8,7 @@
 // resources are updated in the background.
 
 // To learn more about the benefits of this model and instructions on how to
-// opt-in, read http://bit.ly/CRA-PWA.
+// opt-in, read http://bit.ly/CRA-PWA
 
 const isLocalhost = Boolean(
   window.location.hostname === 'localhost' ||