escape . in htaccess regex for CSS and JS HTTP headers

.htaccess

@@ -41,7 +41,7 @@ Options -Indexes
         ModPagespeed Off
 </IfModule>
 <IfModule mod_headers.c>
-  <FilesMatch ".(css|js)$">
+  <FilesMatch "\.(css|js)$">
     Header set Cache-Control "max-age=7200, public"
   </FilesMatch>
 </IfModule>