Package should be using a license expression

[thompson-tomo]

Summary

I wish for the nuget packages to have the licence expression property set correctly

Details

The licence expression property should be set to the correct licence type I.e. MIT as this will enable analysis of licences in use to occur in external tools & the license type will be shown in Nuget etc.

[andrueastman]

related to microsoft/kiota-dotnet#219

[baywet]

(let's use the issue in abstractions to discuss the nature of the changes and this issue to track the work here so we don't have a split conversation)