Avoid displaying the translation banner (mysociety#4153)

Author: jonkri

Diff for: templates/web/base/common_header_tags.html

@@ -80,5 +80,7 @@
 <link rel="icon" href="/cobrands/[% c.cobrand.moniker %]/favicon.ico">
 [% END %]
 
+<meta name="google" content="notranslate">
+
 [% INCLUDE 'header_opengraph.html' %]
 [% TRY %][% PROCESS 'header_extra.html' %][% CATCH file %][% END %]