fix(forms): fix typo

Author: kazupon

docs/en/forms.md

@@ -6,7 +6,7 @@ When using Vuex in strict mode, it could be a bit tricky to use `v-model` on a p
 <input v-model="obj.message">
 ```
 
-Assuming `obj` is a computed property that returns an Object from the store, the `v-model` here will attempt to directly mutate `obj.message` when the user types in the input. In strict mode, this will result in en error because the mutation is not performed inside an explicit Vuex mutation handler.
+Assuming `obj` is a computed property that returns an Object from the store, the `v-model` here will attempt to directly mutate `obj.message` when the user types in the input. In strict mode, this will result in an error because the mutation is not performed inside an explicit Vuex mutation handler.
 
 The "Vuex way" to deal with it is binding the `<input>`'s value and call an action on the `input` or `change` event: