Fix letter case in the example for creating the cache secret

Whilst changing the cache credentials to be loaded into init-runner-secrets volume, names of the secret keys were changed to lowercase (accessKey was replaced with accesskey and secretKey with secretkey).

Unfortunately the example in the values.yaml has not been updated, so everyone following those instructions and using cache will stumble upon the issue with pod hanging on initialization of the container (as it happened to me).

This merge request updates the letter case in the values.yaml.