flaky handshake limiting integration test

[marten-seemann]

Handshake tests queuening and accepting connections closes handshaking connections when the server is closed
D:/a/quic-go/quic-go/integrationtests/self/handshake_test.go:429
  [FAILED] in [It] - D:/a/quic-go/quic-go/integrationtests/self/handshake_test.go:461 @ 01/28/24 10:40:35.986
+ [FAILED] [0.064 seconds]
Handshake tests queuening and accepting connections [It] closes handshaking connections when the server is closed
D:/a/quic-go/quic-go/integrationtests/self/handshake_test.go:429

  [FAILED] Expected
      <qerr.TransportErrorCode>: 1
  to equal
      <qerr.TransportErrorCode>: 2
  In [It] at: D:/a/quic-go/quic-go/integrationtests/self/handshake_test.go:461 @ 01/28/24 10:40:35.986

  Full Stack Trace
    github.com/quic-go/quic-go/integrationtests/self_test.glob..func10.8.6()
    	D:/a/quic-go/quic-go/integrationtests/self/handshake_test.go:461 +0x6f1