fix: remove version from composer.json

Removed version because `composer validate` fails.

```
The version field is present, it is recommended to leave it out if the
package is published on Packagist.
```

Author: smeghead

composer.json

@@ -1,6 +1,5 @@
 {
     "name": "smeghead/php-class-diagram",
-    "version": "1.4.2",
     "description": "A CLI tool that parses the PHP source directory and outputs PlantUML scripts.",
     "type": "library",
     "keywords": [