Update assembly info file for v1.0.0-preview013

[version update]

Author: nfbot

source/nanoFramework.System.Net.Http/Properties/AssemblyInfo.cs

@@ -28,4 +28,4 @@
 // [assembly: AssemblyVersion("1.0.0.0")]
 [assembly: AssemblyVersion("1.0.0.0")]
 [assembly: AssemblyFileVersion("1.0.0.0")]
-[assembly: AssemblyInformationalVersion("1.0.0-preview008")]
+[assembly: AssemblyInformationalVersion("1.0.0-preview013")]