[llvm] [clang] [clang][DependencyScanner] Remove unused -ivfsoverlay files (PR #73734)

[Michael Spencer via cfe-commits]

Bigcheese wrote:

> It's odd to me that tracking is enabled by default. I would have expected tracking be off by default and enabled explicitly for scanning. Similarly, in the modulemap case it could save-and-restore rather than enable the tracking if it was previously off.

It has to be on by default because of PCH. You never know if a PCM will be used for scanning.

https://github.com/llvm/llvm-project/pull/73734