Update gsutil to use gsutil version 4.68

We can't yet upgrade to version 5.x since it's only py3 compatbile and
some builders still rely on running gsutil with py2.

R=gavinmak@google.com

Bug: 1184108
Change-Id: I002cc3625a2184ab42383b88a014c0631d1a33ee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3508516
Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
diff --git a/gsutil.py b/gsutil.py
index 61aaafe..522ddb3 100755
--- a/gsutil.py
+++ b/gsutil.py
@@ -34,7 +34,7 @@
 
 IS_WINDOWS = os.name == 'nt'
 
-VERSION = '4.28'
+VERSION = '4.68'
 
 
 class InvalidGsutilError(Exception):
@@ -166,9 +166,7 @@
   assert sys.platform != 'cygwin'
 
   cmd = [
-      'vpython',
-      '-vpython-spec', os.path.join(THIS_DIR, 'gsutil.vpython'),
-      '--',
+      sys.executable,
       gsutil_bin
   ] + args_opt + args
   return subprocess.call(cmd, shell=IS_WINDOWS)