Update windows git to 2.16.2

Bug: 811681
Change-Id: I2ef7238baececcf87643cba78d72622922ad881c
Reviewed-on: https://chromium-review.googlesource.com/939991
Reviewed-by: Vadim Shtayura <vadimsh@chromium.org>
Reviewed-by: Aaron Gable <agable@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Jao-ke Chin-Lee <jchinlee@chromium.org>

bootstrap/win/manifest.txt

@@ -17,4 +17,4 @@ $VerifiedPlatform windows-386 windows-amd64
 infra/python/cpython/windows-386 version:2.7.6
 
 @Subdir git
-infra/git/windows-${arch} version:2.15.1.2.chromium12
+infra/git/windows-${arch} version:2.16.2.chromium12