[bootstrap/win] Upgrade Python to 2.7.13.

This is followup of
https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/571171/

Bug: 741001
TEST: > gclient version # to update python
TEST: > .\python.bat # start python 2.7.13 correctly
Change-Id: I07e596d3006104ccb1c5fe0fde097a3c29f8a5a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1605541
Auto-Submit: Takuto Ikuta <tikuta@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>

bootstrap/win/manifest.txt

@@ -14,7 +14,7 @@
 $VerifiedPlatform windows-386 windows-amd64
 
 @Subdir python
-infra/python/cpython/windows-386 version:2.7.6
+infra/python/cpython/${platform} version:2.7.13.chromium7
 
 @Subdir git
 infra/git/windows-${arch} version:2.21.0.chromium16