docs: fix wording in "Testing Form" section. (#997)

Author: dennyhong96

docs/guide/essentials/forms.md

@@ -358,7 +358,7 @@ test('fills in the form', async () => {
 
 What happens if your Input component is not that simple? You might be using a UI library, like Vuetify. If you rely on digging inside the markup to find the right element, your tests may break if the external library decides to change their internals.
 
-In such cases you can use set the value directly, using the component instance and `setValue`.
+In such cases you can set the value directly, using the component instance and `setValue`.
 
 Assume we have a form that uses the Vuetify textarea: