Update to fixed vpython wheels.

The previous version was built against a different MSVC runtime than
the Python interpreter on Windows, which is unsafe on Python 2.7.

Note that this will now use a pure-Python implementation of crcmod
on Windows, since there is no packaged wheel available (only an msi,
which we don't currently support repackaging).

Bug: 1297798
Change-Id: I91e4f58cf2b994280c1620fec86dd8638d8a78ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3474820
Auto-Submit: Brian Ryner <bryner@google.com>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Robbie Iannucci <iannucci@chromium.org>

gsutil.vpython

@@ -51,7 +51,7 @@ wheel: <
 
 wheel: <
   name: "infra/python/wheels/cffi/${vpython_platform}"
-  version: "version:1.14.5.chromium.6"
+  version: "version:1.14.5.chromium.7"
 >
 
 wheel: <
@@ -100,5 +100,5 @@ wheel: <
 
 wheel: <
   name: "infra/python/wheels/crcmod/${vpython_platform}"
-  version: "version:1.7.chromium.2"
+  version: "version:1.7.chromium.3"
 >