[llvm] [CI] Make premerge_advisor_explain write comments (PR #166605)

[David Peixotto via llvm-commits]

dmpots wrote:

@boomanaiden154 I'm seeing a build failure in a PR build that looks like it might be related to this change?

https://github.com/llvm/llvm-project/actions/runs/19180796546/job/54836798720?pr=167018

```
  + python /home/gha/actions-runner/_work/llvm-project/llvm-project/.ci/premerge_advisor_explain.py 1f8d5d46df48720973c8312447b1c9a0165213d4 0 *** 167018 /home/gha/actions-runner/_work/llvm-project/llvm-project/build/test-results.zst9icbo.xml /home/gha/actions-runner/_work/llvm-project/llvm-project/ninja.log
  Traceback (most recent call last):
    File "/home/gha/actions-runner/_work/llvm-project/llvm-project/.ci/premerge_advisor_explain.py", line 146, in <module>
      main(
    File "/home/gha/actions-runner/_work/llvm-project/llvm-project/.ci/premerge_advisor_explain.py", line 78, in main
      comment = get_comment(
                ^^^^^^^^^^^^
  TypeError: get_comment() missing 2 required positional arguments: 'pr_number' and 'body'
  Error: Process completed with exit code 1.
```

https://github.com/llvm/llvm-project/pull/166605