cmd/vendor: update vendored golang.org/x/sys/windows

Update to x/sys git revision 074acd46bca67915925527c07849494d115e7c43

This fixes TestFormatMessage and TestExample on windows/arm by pulling
in CL 154560 and CL 154817.

Change-Id: Ic6495fe3072b5bcc7ea68efb3f0be5fc1fe4c238
Reviewed-on: https://go-review.googlesource.com/c/155297


Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>