New scope: pre trigger delay slider mouse roll does x1

sdrbase/gui/glscopenggui.ui

@@ -1525,6 +1525,9 @@ kS/s</string>
        <property name="toolTip">
         <string>Pre-trigger delay</string>
        </property>
+       <property name="pageStep">
+        <number>1</number>
+       </property>
        <property name="orientation">
         <enum>Qt::Horizontal</enum>
        </property>