Allow license header check without CONTRIBUTORS.txt line

[crleonard]

Hi, I wanted to ask about the shared license header check used by the Swift packages.

In apple/swift-log, CONTRIBUTORS.txt was removed as part of the repository cleanup in apple/swift-log#451, following apple/swift-log#450.

I opened a follow-up PR to remove the remaining stale CONTRIBUTORS.txt references from source/test/benchmark file headers:

apple/swift-log#452

However, that PR was closed for now because the shared license header check still expects this line:

// See CONTRIBUTORS.txt for the list of Swift Logging API project authors

Would it be possible to update the shared license header check so repositories can pass without the CONTRIBUTORS.txt line?

This would allow swift-log and similar repositories to remove stale references after deleting CONTRIBUTORS.txt.

Thanks!