[internal-branch.go1.16-vendor] http2: remove PingTimeout from TestTransportPingWhenReading

Use the default PingTimeout since it has no bearing on the test. A small
value can cause a failure on slower machines. Rely on the deadline to
determine a sufficient amount of time to complete.

Updates golang/go#49076

Change-Id: I9389777fa00ed5193f1fc7ae04d2e2134114c675
Reviewed-on: https://go-review.googlesource.com/c/net/+/352970
Reviewed-by: Bryan C. Mills <[email protected]>
Trust: Bryan C. Mills <[email protected]>
Trust: Brad Fitzpatrick <[email protected]>
Run-TryBot: Bryan C. Mills <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-on: https://go-review.googlesource.com/c/net/+/356987
Trust: Damien Neil <[email protected]>
Run-TryBot: Damien Neil <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>

Author: fraenkel

http2/transport_test.go

@@ -3437,7 +3437,6 @@ func TestTransportPingWhenReading(t *testing.T) {
 func testTransportPingWhenReading(t *testing.T, readIdleTimeout, deadline time.Duration, expectedPingCount int) {
 	var pingCount int
 	ct := newClientTester(t)
-	ct.tr.PingTimeout = 10 * time.Millisecond
 	ct.tr.ReadIdleTimeout = readIdleTimeout
 
 	ctx, cancel := context.WithTimeout(context.Background(), deadline)