Revert net6.0 due to unsupported github action

Author: jburnett

AMT.LinqExtensions/AMT.LinqExtensions.csproj

@@ -16,7 +16,7 @@
     <GenerateNeutralResourcesLanguageAttribute />
 
     <Description>A few LINQ Extensions we find useful.</Description>
-    <PackageReleaseNotes>Supports .NET Core 3.1, .NET 5.0 &amp; 6.0</PackageReleaseNotes>
+    <PackageReleaseNotes>Supports .NET Core 3.1 &amp; .NET 5.0</PackageReleaseNotes>
     <PackageLicenseExpression>Apache-2.0</PackageLicenseExpression>
     <PackageProjectUrl>https://github.com/AltaModaTech/LINQExtensions</PackageProjectUrl>
     <PackageTags>LINQ</PackageTags>
@@ -29,7 +29,7 @@
   .NET Core 1.1 EOL 6/27/2019
 -->
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.1;net5.0;net6.0</TargetFrameworks>
+    <TargetFrameworks>netstandard2.1;net5.0</TargetFrameworks>
   </PropertyGroup>
 
 </Project>

test/test.csproj

@@ -13,7 +13,7 @@
   .NET Core 1.1 EOL 6/27/2019
 -->
   <PropertyGroup>
-      <TargetFrameworks>netcoreapp3.1;net5.0;net6.0</TargetFrameworks>
+      <TargetFrameworks>netcoreapp3.1;net5.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>