add nuget to cake as a tool

Author: TGP

build.cake

@@ -1,6 +1,5 @@
 #tool "dotnet:?package=GitVersion.Tool&version=5.8.1"
 #tool "dotnet:?package=coveralls.net&version=3.0.0"
-#addin nuget:?package=NuGet.CommandLine.XPlat&version=6.0.0
 #tool nuget:?package=NuGet.CommandLine.XPlat&version=6.0.0
 #addin nuget:?package=Cake.Json&version=4.0.0
 #addin nuget:?package=Newtonsoft.Json