Auto merge of #110403 - klensy:bolt-deprecate, r=albertlarsan68,Kobzol

bolt: remove deprecated option value for split-functions

Noticed warning at https://github.com/rust-lang-ci/rust/actions/runs/4711883459/jobs/8356538964#step:26:40828, option value was removed at llvm/llvm-project@96f6ec5.

bolt only running on latest supported llvm (yes?), so it's safe to apply this patch.
cc `@Kobzol`

Author: bors