Let windows with wxWANTS_CHARS have TAB presses under Mac

This notably fixes the use of TAB in wxStyledTextCtrl, where it's
supposed to be handled by the control itself and not as a navigation
key, but is more general than this.

Fixes a regression from 8bca6de.

Closes wxWidgets#17999.

src/osx/cocoa/window.mm

@@ -3552,8 +3552,9 @@ new wxCocoaGesturesImpl(this, m_osxView, eventsMask)
 
 bool wxWidgetCocoaImpl::ShouldHandleKeyNavigation(const wxKeyEvent &WXUNUSED(event)) const
 {
-    // Only controls that intercept tabs for different behavior should return false (ie wxTE_PROCESS_TAB)
-    return true;
+    // If the window wants to have all keys, let it have it and don't process
+    // TAB as key navigation event.
+    return !m_wxPeer->HasFlag(wxWANTS_CHARS);
 }
 
 bool wxWidgetCocoaImpl::DoHandleKeyNavigation(const wxKeyEvent &event)