Adjust retransmission credit after PING gets sent in QuicSentPacketManagerTest.ClearLastInflightPacketsSentTime.
Adjust retransmission credit after PING gets sent in QuicSentPacketManagerTest.ClearLastInflightPacketsSentTime.

PiperOrigin-RevId: 313652894
Change-Id: I23e9cf3e09b354fe459bc58265356fa90094c664

google/quiche,google/quiche,google/quiche,google/quiche