Fix regression in mouse click event handling in wxSTC

In EVT_RIGHT_DOWN event handler introduced in 68888ca0a2 we need to propagate event to process it further in EVT_RIGHT_UP handler. This is important especially for wxGTK and wxOSX where EVT_RIGHT_UP is used to generate a context menu event.

Closes #17817.

interface/wx/stc/stc.h

@@ -6413,6 +6413,10 @@ public:
 
         The input should be one of the
         @link wxStyledTextCtrl::wxSTC_POPUP_NEVER wxSTC_POPUP_* @endlink constants.
+        @remarks
+        When wxContextMenuEvent is used to create a custom popup menu,
+        this function should be called with wxSTC_POPUP_NEVER.  Otherwise both
+        the custom and the default popup menus may be shown.
     */
     void UsePopUp(int popUpMode);