XZS [1] filed a request to merge gnome-shell-extension-hide-titlebar [2] into gnome-shell-extension-maximus-two-git [3]:

hide-titlebar is no longer under active development and not compatible with the current gnome-shell version. maximus-two provides the same functionality and is up to date, so users are advised to switch to it. Merging the packages would reflect this.

[1] https://aur4.archlinux.org/account/XZS/ [2] https://aur4.archlinux.org/pkgbase/gnome-shell-extension-hide-titlebar/ [3] https://aur4.archlinux.org/pkgbase/gnome-shell-extension-maximus-two-git/