Remove unused imports from HaGatewayProviderModule

After merge with main branch, UserConfiguration and ApiAuthenticator
imports are no longer used due to code refactoring. Removing them to
fix checkstyle violations.

- Remove unused import: io.trino.gateway.ha.config.UserConfiguration
- Remove unused import: io.trino.gateway.ha.security.ApiAuthenticator

Author: hpopuri2

gateway-ha/src/main/java/io/trino/gateway/ha/module/HaGatewayProviderModule.java

@@ -40,7 +40,6 @@
 import io.trino.gateway.ha.config.OAuth2GatewayCookieConfigurationPropertiesProvider;
 import io.trino.gateway.ha.config.RoutingRulesConfiguration;
 import io.trino.gateway.ha.config.RulesExternalConfiguration;
-import io.trino.gateway.ha.config.UserConfiguration;
 import io.trino.gateway.ha.config.ValkeyConfiguration;
 import io.trino.gateway.ha.persistence.JdbcConnectionManager;
 import io.trino.gateway.ha.persistence.RecordAndAnnotatedConstructorMapper;
@@ -57,7 +56,6 @@
 import io.trino.gateway.ha.router.RoutingGroupSelector;
 import io.trino.gateway.ha.router.RoutingManager;
 import io.trino.gateway.ha.router.ValkeyDistributedCache;
-import io.trino.gateway.ha.security.ApiAuthenticator;
 import io.trino.gateway.ha.security.AuthorizationManager;
 import io.trino.gateway.ha.security.LbAuthorizer;
 import io.trino.gateway.ha.security.LbFormAuthManager;