[llvm] [NFC][UTC] Avoid copy-paste in `update_analyze_test_checks.py` (PR #178456)

[Andrei Elovikov via llvm-commits]

eas wrote:

> you made functional changes to support VPlan debug output

They depend on `-vplan-print-after*` changes so I can't create a PR yet. I've prepared the changes already though: https://github.com/llvm/llvm-project/commit/cd986aa77d5871abc9be87929682878af33eb245

https://github.com/llvm/llvm-project/pull/178456