Reordered the attribute values of stylesheet_pack_tag.

In Rails 7, `media` is optional and the order of attribute values in stylesheet_link_tag has changed,
so I modified the test code accordingly.

```
Failure:
HelperTest#test_stylesheet_pack_tag [/Users/jun.morita/Documents/repo/simpacker/test/helper_test.rb:12]:
--- expected
+++ actual
@@ -1 +1 @@
-"<link rel=\"stylesheet\" media=\"screen\" href=\"/packs/application.css\" />"
+"<link rel=\"stylesheet\" href=\"/packs/application.css\" media=\"screen\" />"
```

ref: rails/rails#41215

Author: madogiwa0124

test/helper_test.rb

@@ -9,7 +9,7 @@ def test_javascript_pack_tag
   end
 
   def test_stylesheet_pack_tag
-    assert_equal '<link rel="stylesheet" media="screen" href="/packs/application.css" />', stylesheet_pack_tag('application')
+    assert_equal '<link rel="stylesheet" href="/packs/application.css" media="screen" />', stylesheet_pack_tag('application')
   end
 
   def test_image_pack_tag