Change responsive media query to screen only (#23389).

Patch by Felix Gliesche.

git-svn-id: http://svn.redmine.org/redmine/trunk@15778 e93f8b46-1217-0410-a6f0-8f06a7374b81

public/stylesheets/responsive.css

@@ -25,7 +25,7 @@
   add first breakpoint here and start adding responsiveness
 */
 
-@media all and (max-width: 899px)
+@media screen and (max-width: 899px)
 {
   /*----------------------------------------*\
     A) BASIC MOBILE RESETS