Don't make wxAuiFloatingFrame root of a top navigation domain

This allows the accelerators associated with it to propagate to the parent
frame, which is what we want to happen in practice.

Closes #16870.

include/wx/aui/floatpane.h

@@ -43,6 +43,9 @@ public:
     void SetPaneWindow(const wxAuiPaneInfo& pane);
     wxAuiManager* GetOwnerManager() const;
 
+    // Allow processing accelerators to the parent frame
+    virtual bool IsTopNavigationDomain() const { return false; }
+
 protected:
     virtual void OnMoveStart();
     virtual void OnMoving(const wxRect& windowRect, wxDirection dir);