Fix Project Archive Compare E2E Spec

What does this MR do and why?

In the review apps we are seeing #372516 (closed)
Debugging it appears that our HTTP client is sometimes returning a RestClient::Response instead of a RestClient::RawResponse.
The test appears to be written expecting that we call Support::API.get but for some reason this doesn't appear to be the case in all tests.
By being explicit in how we call the method, we can avoid any risk of calling the incorrect get method.

It seems we may have had similar issues in the past such as !30793 (merged) where airborne was interferring with calling QA::Support::Api in some cases. This appears to be the same problem here.

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