[clang] [llvm] [analyzer] Delete `alpha.security.MallocOverflow` (PR #103059)

[Artem Dergachev via cfe-commits]

https://github.com/haoNoQ approved this pull request.

I too think this checker can be safely deleted. To the best of my knowledge, nobody is using it.

https://github.com/llvm/llvm-project/pull/103059