Job Migration should not be dependent of hf-token secret
### Link

_No response_

### Description

Job migration should not require hf token secret :

https://github.com/huggingface/datasets-server/blob/main/chart/templates/jobs/mongodb-migration/job.yaml#L23
https://github.com/huggingface/datasets-server/blob/main/chart/templates/_envCommon.tpl#L9
Job Migration should not be dependent of hf-token secret: ### Link

_No response_

### Description

Job migration should not require hf token secret :

https://github.com/huggingface/datasets-server/blob/main/chart/templates/jobs/mongodb-migration/job.yaml#L23
https://github.com/huggingface/datasets-server/blob/main/chart/templates/_envCommon.tpl#L9