[llvm] Remove a debugging message left in a unit test. (PR #137451)

[Abid Qadeer via llvm-commits]

abidh wrote:

> LLVM Buildbot has detected a new failure on builder `llvm-clang-aarch64-darwin` running on `doug-worker-5` while building `llvm` at step 6 "test-build-unified-tree-check-all".
> 
> Full details are available at: https://lab.llvm.org/buildbot/#/builders/190/builds/19044
> 
> Here is the relevant piece of the build log for the reference

This PR just removes a debugging message from a unit test. There is not any functionality change. I am not sure how this can cause any other test failure.

https://github.com/llvm/llvm-project/pull/137451