Bumping .NET assembly version number before 5.13.2 release as there were changes

Source commit: 404c96e8f75778ae72bad955c02b8af775e096ad

dotnet/properties/AssemblyInfo.cs

@@ -31,7 +31,7 @@ namespace WinSCP
     {
         public const string UndefinedProductVersion = "9.9.9.9";
 
-        public const string Version = "1.5.4.0";
+        public const string Version = "1.5.5.0";
         public const string ProductVersion = "5.13.2.0";
     }
 }