Fix UnobservedTaskException on Http2's SendPingAsync (#64494)

Wrap the SendPingAsync function with LogExceptions in Http2Connection.cs
to avoid any exception here being caught as an UnobservedTaskException.

Fix #64450

Signed-off-by: Shubhanshu Saxena <shubhanshu.e01@gmail.com>

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/Http2Connection.cs

@@ -2038,7 +2038,7 @@ private void VerifyKeepAlive()
                         _keepAlivePingTimeoutTimestamp = now + _keepAlivePingTimeout;
 
                         long pingPayload = Interlocked.Increment(ref _keepAlivePingPayload);
-                        SendPingAsync(pingPayload);
+                        LogExceptions(SendPingAsync(pingPayload));
                         return;
                     }
                     break;