core: Delete stale SuppressWarnings("deprecated") for ATTR_LOAD_BALANCING_CONFIG (#11982)

ATTR_LOAD_BALANCING_CONFIG was deleted in bf7a42d.

Author: ejona86

core/src/main/java/io/grpc/internal/AutoConfiguredLoadBalancerFactory.java

@@ -40,8 +40,6 @@
 import java.util.Map;
 import javax.annotation.Nullable;
 
-// TODO(creamsoup) fully deprecate LoadBalancer.ATTR_LOAD_BALANCING_CONFIG
-@SuppressWarnings("deprecation")
 public final class AutoConfiguredLoadBalancerFactory {
 
   private final LoadBalancerRegistry registry;