chore(privatek8s/infra.ci.jenkins.io): new websites File Share service principal writer credential names

[lemeurherve]

This PR renames website File Share service principal writer credentials so they're the same than the ones used in https://github.com/jenkins-infra/azure/blob/91b75632186a6ab529a858166de84456bf1e87dd/updatecli/values.yaml to ensure consistency and avoid mistakes.

EDIT: duplicating them as a first step, will remove duplicated credentials after updating consumers pipelines.

Follow-up of:

• https://github.com/jenkins-infra/azure/pull/754

Ref:

• https://github.com/jenkins-infra/helpdesk/issues/4149