Roll git to 2.28.0 on Windows

Bug: 1070694
Change-Id: I18d5686738917869ada2ebdd8995d39ed84ec851
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2340256
Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

bootstrap/manifest.txt

@@ -24,4 +24,4 @@ infra/3pp/tools/cpython/${platform} version:2.7.17.chromium.22
 infra/3pp/tools/cpython3/${os}-${arch} version:3.8.0.chromium.8
 
 @Subdir git
-infra/3pp/tools/git/${os}-${arch} version:2.24.1.chromium.5
+infra/3pp/tools/git/${os}-${arch} version:2.28.0.chromium.6

bootstrap/manifest_bleeding_edge.txt

@@ -24,4 +24,4 @@ infra/3pp/tools/cpython/${platform} version:2.7.17.chromium.22
 infra/3pp/tools/cpython3/${os}-${arch=amd64} version:3.8.0.chromium.8
 
 @Subdir git
-infra/3pp/tools/git/${os}-${arch} version:2.24.1.chromium.5
+infra/3pp/tools/git/${os}-${arch} version:2.28.0.chromium.6