Deploy git 2.18 to depot_tools on a bleeding edge.

R=hinoka

Bug: 851505
Change-Id: I3e13da0ec736fb3da4f4a95c71ed07c9a4fd0eca
Reviewed-on: https://chromium-review.googlesource.com/1168130
Reviewed-by: Ryan Tseng <hinoka@chromium.org>
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>

bootstrap/win/manifest_bleeding_edge.txt

@@ -17,4 +17,4 @@ $VerifiedPlatform windows-386 windows-amd64
 infra/python/cpython/${platform} version:2.7.13.chromium7
 
 @Subdir git
-infra/git/windows-${arch} version:2.17.1.chromium15
+infra/git/windows-${arch} version:2.18.0.chromium16