Bump Windows bleeding edge git to 2.8.1

R=dnj@chromium.org
BUG=600028

Review URL: https://codereview.chromium.org/1858083002 .

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@299704 0039d316-1c4b-4281-b951-d872f2087c98

bootstrap/win/win_tools.bat

@@ -69,7 +69,7 @@ reg Query "HKLM\Hardware\Description\System\CentralProcessor\0" | %FIND_EXE% /i
 if not exist "%WIN_TOOLS_ROOT_DIR%\.git_bleeding_edge" (
   set GIT_VERSION=2.7.4
 ) else (
-  set GIT_VERSION=2.7.4
+  set GIT_VERSION=2.8.1
 )
 set GIT_VERSION=%GIT_VERSION%-%OS_BITS%