[llvm] [BOLT] Use Label annotation instead of EHLabel pseudo. NFCI. (PR #70179)

[Job Noorman via llvm-commits]

https://github.com/mtvec commented:

We might want to remove it from [`RISCVMCPlusBuilder`](https://github.com/llvm/llvm-project/blob/e7012ba8d36f8a38ab58edccf7267f12266218ab/bolt/lib/Target/RISCV/RISCVMCPlusBuilder.cpp#L323) as well while we're at it.

https://github.com/llvm/llvm-project/pull/70179