Replace references to colleagues who have left

[snim2]

This may not be exhaustive:

❯ git grep Apostolou
src/contributing/managing-the-playbook.md:93:* Poss Apostolou - [Staff handbook](/staff-handbook/)

❯ git grep "Technical Director"
src/tech/dealing-with-an-incident.md:25:  * Inform the Technical Director, Head of Technical Operations, and DPO if there

src/tech/dealing-with-an-incident.md:206:If the incident is critical, then you should let the Technical Director (James)

src/tech/support-and-on-call.md:39:You can also use Opsgenie to escalate an alert to them if you are unsure what to do, lack access, or need a hand in general. If it’s a major incident you may want to escalate so that they can deal with client communications. If the person on the second line rota does not respond feel free to escalate the alert to the Head of Technical Operations or the Technical Director to help you. You should also feel free to contact other members of the team if the incident is serious enough and you have discussed it with the person you have escalated to.

src/tech/support-and-on-call.md:56:If you feel that you need a rest from being on call out of hours after a disrupted night of s

[snim2]

The first of those no longer exists, but Technical Director still appears in text about support and incidents.