chore(docs): update license year

Author: 100stacks

docs/_templates/application.njk

@@ -140,7 +140,7 @@
 
   <footer id="foot" class="hxRow hxGutterless">
     <div class="hxCol">
-      &copy; 2017-2020 Rackspace US, Inc.
+      &copy; 2017-2021 Rackspace US, Inc.
       <nav>
         <a href="https://www.rackspace.com/information/legal/websiteterms">Website Terms</a>
         <a href="https://www.rackspace.com/information/legal/privacystatement">Privacy Policy</a>