update `TestCivicGksPredictiveAssertion` once we have an actual approved predictive assertion that is submitted to clinvar

[korikuzma]

side note: I think we should make an issue to update the TestCivicGksPredictiveAssertion class in civicpy/tests/test_exports.py once we have an actual approved predictive assertion that is submitted to clinvar (which might be a while because there are currently not assertions that meet all of the criteria for clinvar submission). This would allow us to remove all the patching we are currently doing in those tests.

Originally posted by @susannasiebert in #227 (comment)