[clang] [clang/APINotes] Fix assertion crash in addObjCMethod for protocol DesignatedInit methods (PR #183799)

[Gábor Horváth via cfe-commits]

https://github.com/Xazax-hun commented:

Overall, it looks good to me! I think the test could be improved a bit. 

https://github.com/llvm/llvm-project/pull/183799