Enable overlay scrollbars in Chromium (#14456)

* Enable overlay scrollbars in Chromium

* Test overlay scrollbar migration

* Simplify Chromium overlay scrollbar migration

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Co-authored-by: David Heinemeier Hansson <david@hey.com>

config/chromium-flags.conf

@@ -1,5 +1,5 @@
 --ozone-platform=wayland
 --ozone-platform-hint=wayland
 --password-store=gnome-libsecret
---enable-features=TouchpadOverscrollHistoryNavigation
+--enable-features=TouchpadOverscrollHistoryNavigation,OverlayScrollbar
 --load-extension=/usr/share/omarchy/default/chromium/extensions/copy-url,/usr/share/omarchy/default/chromium/extensions/yt-dlp,/usr/share/omarchy/default/chromium/extensions/whatsapp-slim