[llvm] [LoopUnroll][NFCI] Clean up remainder followup metadata handling (PR #165272)

[Joel E. Denny via llvm-commits]

jdenny-ornl wrote:

> LLVM Buildbot has detected a new failure on builder `clang-aarch64-quick` running on `linaro-clang-aarch64-quick` while building `llvm` at step 5 "ninja check 1".
> 
> Full details are available at: https://lab.llvm.org/buildbot/#/builders/65/builds/24723

The next run is green.  Looks like a flaky bot or test.

https://github.com/llvm/llvm-project/pull/165272