[llvm] [llvm][SLPVectorizer] Fix a bad cast assertion (PR #97621)

[Jon Roelofs via llvm-commits]

jroelofs wrote:

> @alexey-bataev changed the title

FWIW, the Developer Policy still [allows](https://llvm.org/docs/DeveloperPolicy.html#commit-messages) such links in commit messages.

https://github.com/llvm/llvm-project/pull/97621