Update version number to 0.23.1

Author: Edward Thomson

LibGit2Sharp/Properties/AssemblyInfo.cs

@@ -42,6 +42,6 @@
 // by using the '*' as shown below:
 // [assembly: AssemblyVersion("1.0.*")]
 
-[assembly: AssemblyVersion("0.23.0")]
-[assembly: AssemblyFileVersion("0.23.0")]
-[assembly: AssemblyInformationalVersion("0.23.0-dev00000000000000")]
+[assembly: AssemblyVersion("0.23.1")]
+[assembly: AssemblyFileVersion("0.23.1")]
+[assembly: AssemblyInformationalVersion("0.23.1-dev00000000000000")]