Windows SDK requirement changes with 3626 branch

[Marshall Greenblatt]

Chromium/CEF can now be built with Windows SDK versions 10.0.17134 or 10.0.17763 starting with 3626 branch (Chromium version 72.0.3626.0).

From the Chromium commit:

Remove the 10.0.17134 SDK requirement for building Chromium

Until recently Chrome required the 10.0.17134 SDK to build because it
needed declarations from that SDK and there was no more recent SDK. Now
there is a more recent (10.0.17763) SDK which can also build Chrome and
the 10.0.17134 requirement is annoying.

Removing the requirement for a specific version means that some new
Chromium developer might try building with an *older* version, but that
is unlikely, and they will hit errors and will then just need to install
the latest. That is better than forcing developers to install an old SDK
version.