Fix docker setup with InfluxDB

What does this MR do?

When setting up a fresh docker environment (pulling new images etc), it broke down trying to communicate with InfluxDB in PHP code. Looking at InfluxDB's container logs, I saw it was complaining about its CLI args. Turns out I got InfluxDB 2, which is very different.

This MR pins the InfluxDB version we use to 1.8 to avoid this from happening :)

How confident are you it won't break things if deployed?

dev setup only, fixes said setup

Links to related issues

How to test

scripts/start, and see if it (still) works

Checklist

• no test needed
• no unrelated changes
• asked someone for a code review
• set a "for:" label to indicate who will be affected by this change
• used "state:" labels to track this MR's state until it was beta tested
• added to the next milestone (see https://gitlab.com/foodsharing-dev/foodsharing/-/milestones, unless it has a "for:Dev" label)
• added an entry to CHANGELOG.md