[FLINK-37657] Fix default image repository in Helm chart

[nickcaballero]

What is the purpose of the change

Fix default image repository in Helm chart.

Brief change log

• Fix default image repository in Helm chart

Verifying this change

N/A.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changes to the CustomResourceDescriptors: no
• Core observer or reconciler logic that is regularly executed: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable