gfe-relnote: Let QUIC client drops initial key when a handshake packet has been sent. protected by existing gfe2_reloadable_flag_quic_enable_version_draft_25_v3 and gfe2_reloadable_flag_quic_enable_version_draft_27. PiperOrigin-RevId: 308882771 Change-Id: Icbae03467ebc7845dacb8d6398cd2657dcf11632