docs: fix snippets of codes in usage guide (#1496)

Author: tarikjabiri

docs/guide/usage.md

@@ -142,7 +142,7 @@ Let's refactor our current code:
 import { faker } from '@faker-js/faker';
 
 function createRandomUser(): User {
-  const sex = this.faker.person.sexType();
+  const sex = faker.person.sexType();
   const firstName = faker.person.firstName(sex);
   const lastName = faker.person.lastName();
   const email = faker.internet.email(firstName, lastName);
@@ -179,7 +179,7 @@ Faker has your back, with another helper method:
 import { faker } from '@faker-js/faker';
 
 function createRandomUser(): User {
-  const sex = this.faker.person.sexType();
+  const sex = faker.person.sexType();
   const firstName = faker.person.firstName(sex);
   const lastName = faker.person.lastName();
   const email = faker.helpers.unique(faker.internet.email, [