move attribution of F# Software Foundation to package description (#7370)

Due to internal package publishing policies, the author of a package
published via a Microsoft account must be exactly 'Microsoft'.  To preserve
attribution to the F# Software Foundation, mention is made in the <description>
tag of FSharp.Core.

Author: brettfo

eng/targets/Settings.props

@@ -2,7 +2,6 @@
 
   <PropertyGroup>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
-    <Authors>Microsoft and F# Software Foundation</Authors>
     <PackageTags>Visual F# Compiler FSharp functional programming</PackageTags>
     <NuspecBasePath>$(ArtifactsBinDir)</NuspecBasePath>
   </PropertyGroup>

src/fsharp/FSharp.Core.nuget/FSharp.Core.nuget.csproj

@@ -6,7 +6,7 @@
     <PackageId>FSharp.Core</PackageId>
     <NuspecFile>FSharp.Core.nuspec</NuspecFile>
     <IsPackable>true</IsPackable>
-    <PackageDescription>FSharp.Core redistributables from Visual F# Tools version $(FSPackageMajorVersion) For F# $(FSCoreMajorVersion)</PackageDescription>
+    <PackageDescription>FSharp.Core redistributables from Visual F# Tools version $(FSPackageMajorVersion) For F# $(FSCoreMajorVersion).  Contains code from the F# Software Foundation.</PackageDescription>
   </PropertyGroup>
 
   <ItemGroup>