Remove multipath_enabled from quic_config and quic_connection. No functional change expected.

net/tools/quic/end_to_end_test.cc

Index: net/tools/quic/end_to_end_test.cc
diff --git a/net/tools/quic/end_to_end_test.cc b/net/tools/quic/end_to_end_test.cc
index 9a7ca65cde1163f0afc96524351def15fa0b15f8..cfb5f3168ae125353e97ee8438619e3bb9bc0784 100644
--- a/net/tools/quic/end_to_end_test.cc
+++ b/net/tools/quic/end_to_end_test.cc
@@ -1322,9 +1322,6 @@ TEST_P(EndToEndTest, SetIndependentMaxIncomingDynamicStreamsLimits) {
 
 TEST_P(EndToEndTest, NegotiateCongestionControl) {
   FLAGS_quic_reloadable_flag_quic_allow_new_bbr = true;
-  // Disable this flag because if connection uses multipath sent packet manager,
-  // static_cast here does not work.
-  FLAGS_quic_reloadable_flag_quic_enable_multipath = false;
   ASSERT_TRUE(Initialize());
   EXPECT_TRUE(client_->client()->WaitForCryptoHandshakeConfirmed());
 
@@ -2205,7 +2202,7 @@ TEST_P(EndToEndTest, BadEncryptedData) {
 
   std::unique_ptr<QuicEncryptedPacket> packet(ConstructEncryptedPacket(
       client_->client()->session()->connection()->connection_id(), false, false,
-      false, 1, "At least 20 characters.", PACKET_8BYTE_CONNECTION_ID,
+      1, "At least 20 characters.", PACKET_8BYTE_CONNECTION_ID,
       PACKET_6BYTE_PACKET_NUMBER));
   // Damage the encrypted data.
   string damaged_packet(packet->data(), packet->length());