net/http: remove arbitrary timeout in TestServerHijackGetsBackgroundByte_big

This test fails with "timeout" once per couple of months.
It may be that the arbitrary timeout is too short,
or it may be that the test is detecting a real bug
(perhaps a deadlock) and reporting it without sufficient
information to debug.

Either way, the arbitrary timeout is doing only harm:
either it is too short, or it is preventing us from getting
a useful goroutine dump when the test inevitably times out.

Fixes #35498 (hopefully).

Change-Id: Ic6bbb1ef8df2c111b9888ba9903f58633e7cb95d
Reviewed-on: https://go-review.googlesource.com/c/go/+/369854
Trust: Bryan Mills <[email protected]>
Run-TryBot: Bryan Mills <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-by: Damien Neil <[email protected]>

Author: Bryan C. Mills

src/net/http/serve_test.go

@@ -5998,11 +5998,7 @@ func TestServerHijackGetsBackgroundByte_big(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	select {
-	case <-done:
-	case <-time.After(2 * time.Second):
-		t.Error("timeout")
-	}
+	<-done
 }
 
 // Issue 18319: test that the Server validates the request method.