HelmChart ValuesFile no longer accepts relative path in GitRepository

[hiddeco]

Regression bug introduced in #178 and reported on Slack.

During the refactor review the detail of the ValuesFile was missed, and part of the functionality got lost:

	// Alternative values file to use as the default chart values, expected to be a
	// relative path in the SourceRef. Ignored when omitted.
	// +optional
	ValuesFile string `json:"valuesFile,omitempty"`

Resulting in the following for valuesFile: ./infrastructure/vault/values-vault-operator.yaml:

NAMESPACE       NAME                                    READY   MESSAGE       REVISION  SUSPENDED
infra-system    infra-system-vault-operator             False   failed to locate override values file: values-vault-operator.yaml False