also support LTS framework for Connections.Abstractions (#59219)

Author: DeagleGross

src/Servers/Connections.Abstractions/src/Microsoft.AspNetCore.Connections.Abstractions.csproj

@@ -1,8 +1,8 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <Description>Core components of ASP.NET Core networking protocol stack.</Description>
-    <TargetFrameworks>$(DefaultNetFxTargetFramework);netstandard2.0;netstandard2.1;$(DefaultNetCoreTargetFramework)</TargetFrameworks>
+    <TargetFrameworks>$(DefaultNetFxTargetFramework);netstandard2.0;netstandard2.1;$(DefaultNetCoreTargetFramework);$(CurrentLtsTargetFramework)</TargetFrameworks>
     <TargetFrameworks Condition="'$(DotNetBuildSourceOnly)' == 'true'">$(DefaultNetCoreTargetFramework)</TargetFrameworks>
     <IsAspNetCoreApp>true</IsAspNetCoreApp>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>