[lldb][test] TestFunctionTemplateParameterPack.py: XFAIL instead of skip This test doesn't trigger an assertion on top-of-tree. Turn this into an XFAIL instead. Found this test because I'm working on improving parameter pack support in the expression evaluator. GitOrigin-RevId: 42764ec59bc41979663a291fec1c5afdcf0b3fe8