[llvm] [llvm-objdump] Relax directory prefix check in source-interleave test (NFC) (PR #93789)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> (NFC) 

This is good, but I think `[test] ` is more popular for pure test changes.  `NFC` can describe code changes, while `[test]` is clear it is for tests.

https://github.com/llvm/llvm-project/pull/93789