[bitnami/superset] Fix warnings during deployment

[LucasRakotomalala]

Description of the change

• Removed the items part in beat/deployment.yaml for superset-secrets projected volume
• Removed the items part in flower/deployment.yaml for superset-secrets projected volume
• Removed the items part in init/init-job.yaml for superset-secrets projected volume
• Removed the items part in web/deployment.yaml for superset-secrets projected volume
• Removed the items part in worker/deployment.yaml for superset-secrets projected volume

Benefits

• When deploying Superset, no warnings are displayed in the console

Possible drawbacks

N/A

Applicable issues

• fixes [bitnami/superset] Warnings during deployment #34365

Additional information

Checklist

• Chart version bumped in Chart.yaml according to semver. This is not necessary when the changes only affect README.md files.
• Variables are documented in the values.yaml and added to the README.md using readme-generator-for-helm
• Title of the pull request follows this pattern [bitnami/<name_of_the_chart>] Descriptive title
• All commits signed off and in agreement of Developer Certificate of Origin (DCO)