Previous CL[0] had the paths inside the SDK wrong so did not
correctly find the SetEnv.x64.json files in recent cipd packaged
SDKs. The 'win_sdk' portion was not necessary.

Downloading the cipd packages and verifies the old and new paths:

gci . -File -Recurse | Where-Object {$_.Name -match 'SetEnv.x64.json'}

CPID-----------------\
C:\src\dt\tmp\new-sdk\ Windows Kits\10\bin\SetEnv.x64.json
C:\src\dt\tmp\old-sdk\ win_sdk\bin\SetEnv.x64.json

[0] https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3283800

R=iannucci@chromium.org

Bug: 1250098
Change-Id: I579fd288824ca9014176b7b1c221affd966fb953
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3290913
Commit-Queue: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>