fix(api): tests: restore httpretty after AssertRequestsContextManager
fix(api): tests: restore httpretty after AssertRequestsContextManager

Not doing so breaks the user-friendly exceptions for unexpected requests on the
name servers. Doing so requires access on private httpretty properties.

desec-io/desec-stack,desec-io/desec-stack,desec-io/desec-stack,desec-io/desec-stack