Updated 4.1.0.md for typo

Changed composer.php to composer.json

docs/en/04_Changelogs/4.1.0.md

@@ -137,7 +137,7 @@ After migration the folder structure would look like:
 │           ├── css/ _(exposed in blog composer.json)_
 │           │   └── blog.css
 │           └── composer.json
-└── composer.php
+└── composer.json
 ```
  
 ### Use new `$public` theme set {#public-theme}