[llvm] [RemoveDIs] Fix SIGSEGV caused by splitBasicBlock (PR #90312)

[Orlando Cazalet-Hyams via llvm-commits]

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

I was going to ask if the unittest could be changed to use the new textual format, but this (intrinsics) matches the other tests so that's ok for now, that can be updated with the others when we get to that.

Code change makes sense. LGTM once the inline comment is addressed. Thank you!

https://github.com/llvm/llvm-project/pull/90312