Try enable all multiple HTTP/2 connections tests on the new scheduling logic

It enables all disabled multiple HTTP/2 connection tests to check if it now work on the new connection scheduling logic introduced by #53851.

Author: alnikola

src/libraries/System.Net.Http/tests/FunctionalTests/SocketsHttpHandlerTest.cs

@@ -2078,7 +2078,6 @@ public sealed class SocketsHttpHandlerTest_Http2 : HttpClientHandlerTest_Http2
         public SocketsHttpHandlerTest_Http2(ITestOutputHelper output) : base(output) { }
 
         [ConditionalFact(nameof(SupportsAlpn))]
-        [ActiveIssue("https://github.com/dotnet/runtime/issues/41078")]
         public async Task Http2_MultipleConnectionsEnabled_ConnectionLimitNotReached_ConcurrentRequestsSuccessfullyHandled()
         {
             const int MaxConcurrentStreams = 2;
@@ -2119,7 +2118,6 @@ public async Task Http2_MultipleConnectionsEnabled_ConnectionLimitNotReached_Con
         }
 
         [ConditionalFact(nameof(SupportsAlpn))]
-        [ActiveIssue("https://github.com/dotnet/runtime/issues/45204")]
         public async Task Http2_MultipleConnectionsEnabled_InfiniteRequestsCompletelyBlockOneConnection_RemaningRequestsAreHandledByNewConnection()
         {
             const int MaxConcurrentStreams = 2;
@@ -2214,7 +2212,6 @@ public async Task Http2_MultipleConnectionsEnabled_OpenAndCloseMultipleConnectio
 
         [ConditionalFact(nameof(SupportsAlpn))]
         [OuterLoop("Incurs long delay")]
-        [ActiveIssue("https://github.com/dotnet/runtime/issues/43877")]
         public async Task Http2_MultipleConnectionsEnabled_IdleConnectionTimeoutExpired_ConnectionRemovedAndNewCreated()
         {
             const int MaxConcurrentStreams = 2;