runtime: delete unused use_eds_cache_for_ads (#45079)

Change-Id: I432cb1d8bc7d8463a0f7e134de8ba84f44a32fbb

Commit Message: the flag is not used so can be deleted
Additional Description:
Risk Level: low
Testing:
Docs Changes:
Release Notes:
Platform Specific Features:

Signed-off-by: Kuat Yessenov <kuat@google.com>

Author: kyessenov

source/common/runtime/runtime_features.cc

@@ -121,7 +121,6 @@ RUNTIME_GUARD(envoy_reloadable_features_xds_failover_to_primary_enabled);
 RUNTIME_GUARD(envoy_reloadable_features_xds_legacy_delta_skip_subsequent_node);
 RUNTIME_GUARD(envoy_restart_features_move_locality_schedulers_to_lb);
 RUNTIME_GUARD(envoy_restart_features_raise_file_limits);
-RUNTIME_GUARD(envoy_restart_features_use_eds_cache_for_ads);
 RUNTIME_GUARD(envoy_restart_features_validate_http3_pseudo_headers);
 RUNTIME_GUARD(envoy_restart_features_worker_threads_watchdog_fix);
 // Begin false flags. Most of them should come with a TODO to flip true.

test/integration/ads_integration_test.cc

@@ -817,7 +817,6 @@ TEST_P(AdsIntegrationTest, CdsKeepEdsAfterWarmingFailure) {
 
 TEST_P(AdsIntegrationTest, CdsKeepEdsDropOverloadAfterWarmingFailure) {
   // This test should be kept after the runtime guard is deprecated
-  config_helper_.addRuntimeOverride("envoy.restart_features.use_eds_cache_for_ads", "true");
   initialize();
   EXPECT_TRUE(compareDiscoveryRequest(Config::TestTypeUrl::get().Cluster, "", {}, {}, {}, true));
   envoy::config::cluster::v3::Cluster cluster = buildCluster("cluster_0");