activation: don't add the active window to should_get_focus list

The matching X11 focusIn event will never arrive, and so the window is stuck
in the list and messes with activation until it's no longer the active window
and then active later again

BUG: 484155

src/activation.cpp

@@ -557,6 +557,10 @@ void Workspace::gotFocusIn(const Window *window)
 
 void Workspace::setShouldGetFocus(Window *window)
 {
+    if (m_activeWindow == window) {
+        // the matching focusIn event will never arrive
+        return;
+    }
     should_get_focus.append(window);
     updateStackingOrder(); // e.g. fullscreens have different layer when active/not-active
 }