Use simple regex in quic_connection_test.cc

GoogleTest as used in Chromium only supports the "simple" regex syntax described in https://github.com/google/googletest/blob/main/docs/advanced.md#regular-expression-syntax

In particular, it doesn't support grouping.

Use "simple" regexes instead.

PiperOrigin-RevId: 528673454

quiche/quic/core/quic_connection_test.cc

diff --git a/quiche/quic/core/quic_connection_test.cc b/quiche/quic/core/quic_connection_test.cc
index 9858f0b..8fa8d2f 100644
--- a/quiche/quic/core/quic_connection_test.cc
+++ b/quiche/quic/core/quic_connection_test.cc
@@ -17531,7 +17531,7 @@
       QuicConnectionPeer::GetPacketCreator(&connection_), 1);
   if (!GetQuicReloadableFlag(quic_send_ect1)) {
     EXPECT_QUIC_BUG(connection_.OnInFlightEcnPacketAcked(),
-                    "Unexpected call to OnInFlightEcnPacketAcked()");
+                    "Unexpected call to OnInFlightEcnPacketAcked\\(\\)");
     return;
   } else {
     connection_.OnInFlightEcnPacketAcked();
@@ -17556,7 +17556,7 @@
   EXPECT_EQ(per_packet_options.ecn_codepoint, ECN_ECT1);
   if (!GetQuicReloadableFlag(quic_send_ect1)) {
     EXPECT_QUIC_BUG(connection_.OnInvalidEcnFeedback(),
-                    "Unexpected call to OnInvalidEcnFeedback().");
+                    "Unexpected call to OnInvalidEcnFeedback\\(\\)\\.");
     return;
   } else {
     connection_.OnInvalidEcnFeedback();