Remove unsupported SDK targets (#3193)

* yee old sdks (and CI cache too since it's pretty useless)

* also bump deps

* Update src/Discord.Net.Interactions/Discord.Net.Interactions.csproj

Co-authored-by: d4n <dan3436@hotmail.com>

* Update src/Discord.Net.Core/Discord.Net.Core.csproj

Co-authored-by: d4n <dan3436@hotmail.com>

* `.ForEachAsync` => `await foreach`

* remove old targets from .nuspec & update docs

* bump sdk in ws4net provider (probably should deprecate it tho)

---------

Co-authored-by: d4n <dan3436@hotmail.com>

Discord.Net.targets

@@ -28,7 +28,6 @@
         <NoWarn>$(NoWarn);CS1573;CS1591</NoWarn>
         <WarningsAsErrors>true</WarningsAsErrors>
         <GenerateDocumentationFile>true</GenerateDocumentationFile>
-		<RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
     </PropertyGroup>
     <ItemGroup>
         <None Include="../../docs/marketing/logo/PackageLogo.png" Pack="true" PackagePath=""/>