[EE] QA::Page::Component::Dropzone#initialize needs a QA::Page::Base object

What does this MR do?

Fixes an issue introduced by https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16805.

Are there points in the code the reviewer needs to double check?

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16805 was a CE MR, thus the ee:geo QA job was skipped: https://gitlab.com/gitlab-org/gitlab-qa/-/jobs/50344572. That's why we didn't see the error at that time.

Does this MR meet the acceptance criteria?

• Review
  • Has been reviewed by Backend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

Fixes gitlab-qa#173 (closed).