[C] fix: ADO CI spuriously failing format check due to picking up NuGet.config (#28064)
### Description & Motivation
On ADO CI we modify `/NuGet.config` to add an authenticated feed.
This trips up some format checks, which mistakenly considers unformatted
b/c git reports it as dirty.
Scope to just the CWD and below to avoid picking up `/NuGet.config`.