Fix Content-Disposition not working for Azure in API download

What does this MR do and why?

In GitLab 17.1 !155013 (merged) introduced a fix that attempted to send the response-content-disposition query parameter to object storage providers. gitlab-fog-azure-rm expects this query parameter to be a string instead of a symbol, however.

To fix this issue and be consistent with the CarrierWave downloads via Rails controllers, set response-content-disposition and response-content-type to strings.

Closes #472322 (closed).

MR acceptance checklist

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How to set up and validate locally

1. Configure Azure with consolidated object storage.
2. Be sure to set proxy_download to false.
3. See !155013 (merged).