[#1078] Fix LGTM regression

In ORM 5.6.2.Final, the `IdentifierGenerator` extends `Configurable`
so we can skip some casting and `instance of` checks.

Author: DavideD

hibernate-reactive-core/src/main/java/org/hibernate/reactive/id/impl/ReactiveGeneratorWrapper.java

@@ -48,8 +48,8 @@ public Serializable generate(SharedSessionContractImplementor session, Object ob
 
 	@Override
 	public void registerExportables(Database database) {
-		if (generator instanceof ExportableProducer) {
-			((ExportableProducer) generator).registerExportables( database );
+		if ( generator != null ) {
+			generator.registerExportables( database );
 		}
 		if (reactiveGenerator instanceof ExportableProducer) {
 			((ExportableProducer) reactiveGenerator).registerExportables( database );

hibernate-reactive-core/src/main/java/org/hibernate/reactive/id/impl/ReactiveIdentifierGeneratorFactory.java

@@ -68,9 +68,7 @@ else if ( generator instanceof ReactiveIdentifierGenerator) {
 			throw new MappingException( String.format( "Not an id generator [entity-name=%s]", entityName ) );
 		}
 
-		if ( result instanceof Configurable) {
-			( (Configurable) result ).configure( type, config, serviceRegistry );
-		}
+		result.configure( type, config, serviceRegistry );
 
 		return result;
 	}