Updated composer description to reflect that Coder is not a module anymore.

composer.json

 {
     "name": "drupal/coder",
     "type": "library",
-    "description": "Coder is a library and a module to review Drupal code.",
+    "description": "Coder is a library to review Drupal code.",
     "homepage": "https://drupal.org/project/coder",
     "support": {
         "issues": "https://drupal.org/project/issues/coder",