_includes/head.html: Drop useless meta http-equiv="cleartype" tag

This meta tag is only useful for pre-IE9 era and is now useless.
For example, see the discussion on its removal a decade ago at
https://www.drupal.org/project/drupal/issues/1717090 .
We should not keep it anymore.

Author: hosiet

_includes/head.html

@@ -17,5 +17,3 @@
 
 <!-- For all browsers -->
 <link rel="stylesheet" href="{{ base_path }}/assets/css/main.css">
-
-<meta http-equiv="cleartype" content="on">