Do not provide fallback to cookie for font size

* This should be already handled by Config class
* Injecting cookie value to CSS could be security risk

Signed-off-by: Michal Čihař <michal@cihar.com>

libraries/Theme.class.php

@@ -490,9 +490,6 @@ class PMA_Theme
         if (!is_null($fs)) {
             return $fs;
         }
-        if (isset($_COOKIE['pma_fontsize'])) {
-            return htmlspecialchars($_COOKIE['pma_fontsize']);
-        }
         return '82%';
     }