Migrating to v1.2: Update meta tag styling

For
ebiwd/EBI-Framework#85 (comment)

sample-site-v1.2/index.html

@@ -47,8 +47,8 @@
   <!-- If you have a custom header image or colour -->
   <!--
   -->
-  <meta name="ebi:localmasthead-color" content="#000" />
-  <meta name="ebi:localmasthead-image" content="https://www.ebi.ac.uk/web_guidelines/EBI-Framework/v1.2/images/backgrounds/embl-ebi-background.jpg" />
+  <meta name="ebi:masthead-color" content="#000" />
+  <meta name="ebi:masthead-image" content="https://www.ebi.ac.uk/web_guidelines/EBI-Framework/v1.2/images/backgrounds/embl-ebi-background.jpg" />
 
     <!-- you can replace this with theme-[projectname].css. See http://www.ebi.ac.uk/web/style/colour for details of how to do this -->
   <!-- also inform ES so we can host your colour palette file -->