VS: Use most recently installed Windows 10 SDK.

Using a hard-coded SDK version is a big barrier for new developers.
Using "10" as the SDK version will automatically pick the most
recently installed SDK.

Bug: gn:128
Change-Id: I01e1f810f9300302b8fbe369da01e3221d9e8f81
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/10340
Commit-Queue: Brett Wilson <brettw@chromium.org>
Reviewed-by: Brett Wilson <brettw@chromium.org>

src/gn/visual_studio_writer.cc

diff --git a/src/gn/visual_studio_writer.cc b/src/gn/visual_studio_writer.cc
index 3717345..6acff14 100644
--- a/src/gn/visual_studio_writer.cc
+++ b/src/gn/visual_studio_writer.cc
@@ -81,7 +81,7 @@
 const char kVersionStringVs2017[] = "Visual Studio 2017";  // Visual Studio 2017
 const char kVersionStringVs2019[] = "Visual Studio 2019";  // Visual Studio 2019
 const char kWindowsKitsVersion[] = "10";                   // Windows 10 SDK
-const char kWindowsKitsDefaultVersion[] = "10.0.17134.0";  // Windows 10 SDK
+const char kWindowsKitsDefaultVersion[] = "10";            // Windows 10 SDK
 
 const char kGuidTypeProject[] = "{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}";
 const char kGuidTypeFolder[] = "{2150E333-8FDC-42A3-9474-1A3956D46DE8}";