Deprecate --gfe2_reloadable_flag_quic_tls_set_signature_algorithm_prefs.

PiperOrigin-RevId: 400996649
diff --git a/quic/core/http/quic_server_session_base.cc b/quic/core/http/quic_server_session_base.cc
index 6c1d617..1f6ec74 100644
--- a/quic/core/http/quic_server_session_base.cc
+++ b/quic/core/http/quic_server_session_base.cc
@@ -292,15 +292,13 @@
         GetQuicFlag(FLAGS_quic_disable_server_tls_resumption);
   }
 
-  if (!GetQuicReloadableFlag(quic_tls_set_signature_algorithm_prefs) ||
-      !crypto_config_ || !crypto_config_->proof_source()) {
+  if (!crypto_config_ || !crypto_config_->proof_source()) {
     return ssl_config;
   }
 
   absl::InlinedVector<uint16_t, 8> signature_algorithms =
       crypto_config_->proof_source()->SupportedTlsSignatureAlgorithms();
   if (!signature_algorithms.empty()) {
-    QUIC_RELOADABLE_FLAG_COUNT_N(quic_tls_set_signature_algorithm_prefs, 1, 2);
     ssl_config.signing_algorithm_prefs = std::move(signature_algorithms);
   }
 
diff --git a/quic/core/quic_flags_list.h b/quic/core/quic_flags_list.h
index acbe982..6b6d3f0 100644
--- a/quic/core/quic_flags_list.h
+++ b/quic/core/quic_flags_list.h
@@ -19,8 +19,6 @@
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_bbr2_no_probe_up_exit_if_no_queue, true)
 // If true and connection option B201 is used, check if cwnd limited before aggregation epoch, instead of ack event, in PROBE_UP phase.
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_bbr2_check_cwnd_limited_before_aggregation_epoch, true)
-// If true, GFE will explicitly configure its signature algorithm preference.
-QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_tls_set_signature_algorithm_prefs, true)
 // If true, QPACK decoder rejects CR, LF, and NULL in field (header) values, and causes the stream to be reset with H3_MESSAGE_ERROR.
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_reject_invalid_chars_in_field_value, true)
 // If true, QUIC will default enable MTU discovery at server, with a target of 1450 bytes.