Get rid of obsolete dokuwiki plugins

We have some old unmaintained dokuwiki plugins, triggering warnings in logs. We may get rid of them.

Some old pages/dokuwiki old revisions can be broken after removing theses plugins, but I'm ok with that.

• https://www.dokuwiki.org/plugin:cellbg : Not used, to remove: Disabled
• https://www.dokuwiki.org/plugin:definitionlist: Not used, to remove: Disabled
• https://www.dokuwiki.org/plugin:dl: Used It is used on https://docs.xfce.org/xfce/getting-started for example (Usage of ? / !. Maybe we can use standard "lists" ?
• https://gitlab.xfce.org/www/wiki.xfce.org/-/blob/master/lib/plugins/xfcesubs/: To catch XfceBug and XfceSvnRev patterns. To remove! Disabled
• https://gitlab.xfce.org/www/wiki.xfce.org/-/blob/master/lib/plugins/xfcedocs/: Not sure to understand what it do. Seems to strong the text if started with {gui or {key . It seems that it catch the <figure patterns too ?

I don't understand xfcedocs purpose. But it is still used on recent pages, like https://docs.xfce.org/xfce/getting-started (search for <figure)

ping @kevinbowen :)

Wow, ok, the old dl plugin (not updated since 2008) is used for example on https://docs.xfce.org/xfce/getting-started for the component list:

? Panel
! In a default session there is a full width panel at the top of the screen and a smaller one at the bottom. The [[.:xfce4-panel:|Panel]] application manages all panels on the screen.
! The top panel shows a graphical pager with a miniature view of all workspaces, a task list showing all applications running on the current workspace and a system tray to show status icons that are used for example by some media players or instant messaging applications.
! The bottom panel contains several application launchers and a clock. You can right-click on any panel item to get a menu that allows you to change its properties, add or remove new items or to change the properties of the panel itself.
? Desktop Manager
[...]

I guess this can be replaced by a standard list ?

I've removed the dl & figure syntax from the getting-started page.

For the Panel example, I used a === header and a quote > for each paragraph separated by a blank line.

changed the description