fix: rename storageClass to storageClassName based in docs and comments

[afzouni]

Description

In the values.yaml and README.md, it mentions defining storageClassName to use a custom storageClassName. However, the variable in statefulset.yaml uses storageClass instead. This pull request changes storageClass to storageClassName to ensure consistency and proper functionality.

Issues Resolved

• No specific issue number, but this change addresses the inconsistency between the documentation and the statefulset.yaml file regarding the storageClassName.

Check List

• [* ] Commits are signed per the DCO using --signoff

For any changes to files within Helm chart directories:

• [ ] Helm chart version bumped
• [ ] Helm chart CHANGELOG.md updated to reflect change

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