docs: Minor fix to count docs (#7780)

Small change the docs in order to fix an incorrect ES6 arrow function.

docs/models-usage.md

@@ -334,11 +334,11 @@ Project.findAll({ where: { ... }, raw: true })
 There is also a method for counting database objects:
 
 ```js
-Project.count().then(c)  =>
+Project.count().then(c =>
   console.log("There are " + c + " projects!")
 })
 
-Project.count({ where: {'id': {$gt: 25}} }).then(c)  =>
+Project.count({ where: {'id': {$gt: 25}} }).then(c =>
   console.log("There are " + c + " projects with an id greater than 25.")
 })
 ```