Rename ThirdPartyNotices.txt to THIRD-PARTY-NOTICES.TXT (#8546)

Context: 2081a20

The `ThirdPartyNotices.txt` file included in our NuGet packages was
renamed to `THIRD-PARTY-NOTICES.TXT` in 2081a20.  However, the
change to the build dependencies filename within the repo was never
committed.

Rename the file so that no longer shows up as an untracked file in
the git tree.

Author: pjcollins