Update all bitnami image references to bitnamilegacy for E26

[OFHansen]

Since Bitnami removed their images off Docker Hub, most bitnami images are gone causing issues when trying to pull images that are not cached, this can be solved by switching to bitnamilegacy images.

[igor-soldev]

While switching to bitnamilegacy solves the immediate "pull error", please be aware that Bitnami Legacy images are frozen. They are no longer maintained and will not receive any updates (security patches or bug fixes), which might lead to stability issues down the line for the course exercises.

A sustainable alternative: I suggest using soldevelo/kafka images instead. They are designed as a drop-in replacement (preserving the /opt/bitnami/... structure and env vars) but are actively maintained and free.

Link: https://hub.docker.com/r/soldevelo/kafka-chart