Set an existing Icon name in the Applications' panel desktop file
    
    While we dynamically append --symbolic to the icons while creating
    the sidebar model in
    https://gitlab.gnome.org/GNOME/gnome-control-center/-/blob/master/shell/cc-shell-model.c#L270
    There are automation tools (such as rpmdiff) that parse desktop files
    and verify whether their Icon= matches to an existing file in the
    icon theme package.
    preferences-desktop-apps doesn't exist in adwaita-icon-theme but
    preferences-desktop-apps-symbolic does.