Hide cookie banner from Google search

Implemented on the GOVUK Frontend cookie banner
component in:

alphagov/govuk-frontend#2192

This tells Google to ignore the cookie banner when
it indexes the content of our pages.

app/templates/components/cookie-banner.html

@@ -1,6 +1,6 @@
 {% macro cookie_banner(id='global-cookie-message') %}
 
-<div id="{{ id }}" class="notify-cookie-banner" data-notify-module="cookie-banner" role="region" aria-label="cookie banner">
+<div id="{{ id }}" class="notify-cookie-banner" data-nosnippet data-notify-module="cookie-banner" role="region" aria-label="cookie banner">
   <div class="notify-cookie-banner__wrapper govuk-width-container">
     <h2 class="notify-cookie-banner__heading govuk-heading-m" id="notify-cookie-banner__heading">Can we store analytics cookies on your device?</h2>
     <p class="govuk-body">Analytics cookies help us understand how our website is being used.</p>