Update quic::IsAppleMobile to quic::IsAppleClient for better coverage of Apple related QUIC reverse path validation crash:
1) Added coverage for iOS Youtube (from cr/406134264) & iMM (from Sherlog) user agents.
2) Added coverage for Mac traffic.

The reasoning of this change being:
1) We are not sure if Apple networking stack on Mac has the same bug. But it is safer to cover this portion of traffic as well.
2) Given occasional client crashes are less urgent than server crashes, the current change is not exhaustive but aimed to cover most of the traffic.
3) This change will make IETF port migration fail at Chrome on MAC due to server reverse path validation failure. This is likely to be fine given the port migration feature needs its own binary fix rolled out and this is a small amount of Chrome traffic compared to Windows.

Protected by FLAGS_quic_reloadable_flag_quic_disable_reverse_path_validation_for_apple.

PiperOrigin-RevId: 407085983
diff --git a/quic/core/quic_flags_list.h b/quic/core/quic_flags_list.h
index 9a8f8ad..0b5ada5 100644
--- a/quic/core/quic_flags_list.h
+++ b/quic/core/quic_flags_list.h
@@ -63,8 +63,6 @@
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_disable_version_t051, true)
 // If true, disable blackhole detection on server side.
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_disable_server_blackhole_detection, false)
-// If true, disable reverse path validation for Apple mobile clients.
-QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_disable_reverse_path_validation_for_apple_mobile, false)
 // If true, discard INITIAL packet if the key has been dropped.
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_discard_initial_packet_with_key_dropped, true)
 // If true, do not bundle 2nd ACK with connection close if there is an ACK queued.