fix: Change security context of Redis image to match redis user

[Starkteetje]

Previously, we set the default security context of the Redis to a user/group not taken. This could cause problems with permissions, resulting in error logs and shutdown delays, thus this commit changes the default user/group to reflect the built-in redis user.

Fixes #1764

Description

Checklist

• [x] PR is rebased to/aimed at branch develop
• [x] PR follows Contributing Guide
• [x] Added tests (if necessary)
• [x] Extended README/Documentation (if necessary)
• [x] Adjusted versions of image and Helm chart in Chart.yaml (if necessary)