win-update: Remove legacy CMake file

[tytan652]

Description

Missed in 72428ccd97ae032825fb3b390c0b2b50768655bf and in 42670ab4e3d48d37bb9926f4d8b3b3b0dcfd0a62

Motivation and Context

:facepalm: I checked there is normally no more legacy.cmake files in the repo.

How Has This Been Tested?

find . -iname "legacy.cmake" -print list nothing now.

Types of changes

• Code cleanup (non-breaking change which makes code smaller or more readable)

Checklist:

• [x] My code has been run through clang-format.
• [x] I have read the contributing document.
• [x] My code is not on the master branch.
• [ ] The code has been tested.
• [x] All commit messages are properly formatted and commits squashed where appropriate.
• [x] I have included updates to all appropriate documentation.