Use chunk size of 10MB for pulp uploads

What does this MR do?

The default chunk size used by Pulp content upload commands is 1MB. Let's use chunk size of 10MB, like we do for omnibus-gitlab.

Why was this MR needed?

Improve the performance of pulp upload commands

What's the best way to test this MR?

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-runner/-/work_items/39121