Drop XRandR dependency from Options's currentRefreshRate

Summary:
This code branch was dead. It was for the case that the number of screens
is 0, but KWin::Screens never has a count of zero, especially not the
XRandR based screens (c.f. screens_xrandr.cpp method ::update) which has
a fallback handling setting the count to always 1 if there are no screens.

Test Plan: Compiles

Reviewers: #kwin, #plasma

Subscribers: plasma-devel, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D7650

options.cpp

@@ -31,7 +31,6 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #include "screens.h"
 #include "settings.h"
-#include "xcbutils.h"
 #include <kwinglplatform.h>
 #include <QOpenGLContext>
 
@@ -67,10 +66,6 @@ int currentRefreshRate()
             }
         }
         rate = qRound(Screens::self()->refreshRate(syncScreen)); // TODO forward float precision?
-    } else if (Xcb::Extensions::self()->isRandrAvailable()) {
-        // last restort - query XRandR screenInfo rate - probably wrong on nvidia systems
-        Xcb::RandR::ScreenInfo screenInfo(rootWindow());
-        rate = screenInfo->rate;
     }
 
     // 0Hz or less is invalid, so we fallback to a default rate