Polish "Optimize AutoConfigurationImportSelector.filter()"

See gh-20928

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/AutoConfigurationImportSelector.java

@@ -254,9 +254,9 @@ public class AutoConfigurationImportSelector implements DeferredImportSelector,
 			return configurations;
 		}
 		List<String> result = new ArrayList<>(candidates.length);
-		for (int i = 0; i < candidates.length; i++) {
+		for (String candidate : candidates) {
-			if (candidates[i] != null) {
+			if (candidate != null) {
-				result.add(candidates[i]);
+				result.add(candidate);
 			}
 		}
 		if (logger.isTraceEnabled()) {