Remove time preference dialog title

According to reports on the internet this may make the dialog work in
landscape mode also on devices where it doesn't work with the title.

Fix #277

android_app/app/src/main/java/com/health/openscale/gui/preferences/TimePreferenceDialog.java

@@ -44,6 +44,7 @@ public class TimePreferenceDialog extends DialogPreference {
 
         setPositiveButtonText(R.string.label_ok);
         setNegativeButtonText(R.string.label_cancel);
+        setDialogTitle(null);
         calendar = Calendar.getInstance();
     }