Fix lints

Author: isoos

test/bit_array_test.dart

@@ -1,8 +1,7 @@
 import 'dart:typed_data';
 
-import 'package:test/test.dart';
-
 import 'package:bit_array/bit_array.dart';
+import 'package:test/test.dart';
 
 void main() {
   group('BitArray', () {

test/bit_counter_test.dart

@@ -1,8 +1,7 @@
 import 'dart:math';
 
-import 'package:test/test.dart';
-
 import 'package:bit_array/bit_array.dart';
+import 'package:test/test.dart';
 
 void main() {
   group('BitCounter', () {

test/bit_set_test.dart

@@ -1,6 +1,5 @@
-import 'package:test/test.dart';
-
 import 'package:bit_array/bit_array.dart';
+import 'package:test/test.dart';
 
 void main() {
   group('ListSet', () {

test/composite_counter_test.dart

@@ -1,6 +1,5 @@
-import 'package:test/test.dart';
-
 import 'package:bit_array/bit_array.dart';
+import 'package:test/test.dart';
 
 void main() {
   group('CompositeCounter', () {

test/composite_set_test.dart

@@ -1,6 +1,5 @@
-import 'package:test/test.dart';
-
 import 'package:bit_array/bit_array.dart';
+import 'package:test/test.dart';
 
 void main() {
   group('CompositeSet', () {