Remove unused help button from style manager (fix #14055)

Author: nyalldawson

src/ui/qgsstylev2managerdialogbase.ui

@@ -412,7 +412,7 @@ QMenu::item:selected {  background-color: gray; } */
       <enum>Qt::Horizontal</enum>
      </property>
      <property name="standardButtons">
-      <set>QDialogButtonBox::Close|QDialogButtonBox::Help</set>
+      <set>QDialogButtonBox::Close</set>
      </property>
      <property name="centerButtons">
       <bool>false</bool>