Two key-upload-related tests being blacklisted by synapse

[ShadowJonathan]

When I was looking over SkipIfs in the codebase, I found out that these following tests are explicitly blacklisted on synapse.

https://github.com/matrix-org/complement/blob/d5025cd75007609d52a77535388be9317963aedd/tests/csapi/upload_keys_test.go#L77

https://github.com/matrix-org/complement/blob/d5025cd75007609d52a77535388be9317963aedd/tests/csapi/upload_keys_test.go#L56

Seeing as how these tests are related to data validation on a server's side, I do not understand why Synapse wants to skip them, thus this issue as a nag; Why does Synapse skip these tests?

I want to update the comment with a reason given, or a reference to an issue/discussion about exactly that, or to an issue working towards clearing this skip.