Adwaita: fix devel styling for sidebar apps

- don't put the gradient/cogged wheel on apps that have a split headerbar
  due to having a sidebar
4 jobs for <span class="ref-name">1383-inspector-provide-a-widget-highlighting-for-css-node-tree</span> in 7 minutes and 48 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #117494
fedora-x86_64

00:06:36

passed #117495
win32
msys2-mingw32

00:03:29

 
  Flatpak
canceled #117496
flatpak:demo

00:01:12

canceled #117497
flatpak:widget-factory

00:01:11