Update deprecated Bitnami Kafka references in documentation to ensure tutorials work #9

Hi,

I noticed that the Kafka documentation (MDX files) references bitnami/kafka for both Docker and Helm. Since Bitnami has restricted public access and deprecated legacy charts, users following these tutorials will likely face errors.

Proposed Solution
I suggest updating the examples to use SolDevelo alternatives, which are free, actively maintained, and fully compatible (drop-in replacements).

1. Docker (8-kafka-environmental-isolation.mdx)
Replace bitnami/kafka:latest with:

image: soldevelo/kafka:latest

2. Helm (4-kafka-helm-charts.mdx & 5-kafka-cluster-automation-deployment.mdx)
Update the install command to the OCI registry:
helm install my-kafka oci://registry-1.docker.io/soldevelo/kafka-chart