Deprecate --gfe2_reloadable_flag_quic_check_fallback_null.

PiperOrigin-RevId: 336661349
Change-Id: I3daf83878a9f77a51d82c85f95a0c34146df08c1

quic/core/crypto/quic_crypto_server_config.cc

diff --git a/quic/core/crypto/quic_crypto_server_config.cc b/quic/core/crypto/quic_crypto_server_config.cc
index 3e558d0..e463d24 100644
--- a/quic/core/crypto/quic_crypto_server_config.cc
+++ b/quic/core/crypto/quic_crypto_server_config.cc
@@ -831,8 +831,7 @@
   if (found_error) {
     // If we are already using the fallback config, or there is no fallback
     // config to use, just bail out of the handshake.
-    if ((GetQuicReloadableFlag(quic_check_fallback_null) &&
-         configs.fallback == nullptr) ||
+    if (configs.fallback == nullptr ||
         context->signed_config()->config == configs.fallback ||
         !GetQuicReloadableFlag(
             send_quic_fallback_server_config_on_leto_error)) {