Update preCICE developrs overview picture for 2024

[MakisH]

The suggested picture:

• Puts everyone in one circle, to avoid the feeling that we are disconnected (we are way better connected than other cross-organization projects).
• Sorts the people by "academic age". Puts the PIs on the same level/height.
• Removes the distinction in border colors around each person.
• Removes the student assistants (fluctuating too much, not many at the moment).
• Removes @KyleDavisSA from the current picture (still in the contributors page), adds @carme-hp and @Fujikawas.
• Removes the group names (SCCS / SGS / US3) as they are not so recognizable/explanatory, adds "Prof." and "Jun.-Prof." to PIs.

It is clear that the spacing etc can be improved, but I don't want to invest more time on this at the moment, as the source file has accumulated some chaos. I would rather merge this and remake the picture from scratch later on.