fix: minio tenant values region is broken

[Dankoy]

Error

Error: INSTALLATION FAILED: Tenant.minio.min.io "minio" is invalid: [spec.buckets[0].region: Invalid value: "null": spec.buckets[0].region in body must be of type string: "null", spec.buckets[1].region: Invalid value: "null": spec.buckets[1].region in body must be of type string: "null", spec.buckets[2].region: Invalid value: "null": spec.buckets[2].region in body must be of type string: "null", spec.buckets[3].region: Invalid value: "null": spec.buckets[3].region in body must be of type string: "null", spec.buckets[4].region: Invalid value: "null": spec.buckets[4].region in body must be of type string: "null", spec.buckets[5].region: Invalid value: "null": spec.buckets[5].region in body must be of type string: "null", spec.buckets[6].region: Invalid value: "null": spec.buckets[6].region in body must be of type string: "null", <nil>: Invalid value: "null": some validation rules were not checked because the object was invalid; correct the existing errors to complete validation]

Fix of minio bucket region values