Update testing-environments.md (#2665)

Remove extraneous "both"

content/docs/testing-environments.md

@@ -53,6 +53,6 @@ Sometimes, you may not want to mock timers. For example, maybe you're testing an
 
 ### End-to-end tests {#end-to-end-tests-aka-e2e-tests}
 
-End-to-end tests are useful for testing longer workflows, especially when they're critical to your business (such as payments or signups). For these tests, you'd probably want to test both how a real browser renders the whole app, fetches data from the real API endpoints, uses sessions and cookies, navigates between different links. You might also likely want to make assertions not just on the DOM state, but on the backing data as well (e.g. to verify whether the updates have been persisted to the database).
+End-to-end tests are useful for testing longer workflows, especially when they're critical to your business (such as payments or signups). For these tests, you'd probably want to test how a real browser renders the whole app, fetches data from the real API endpoints, uses sessions and cookies, navigates between different links. You might also likely want to make assertions not just on the DOM state, but on the backing data as well (e.g. to verify whether the updates have been persisted to the database).
 
 In this scenario, you would use a framework like [Cypress](https://www.cypress.io/) or a library like [puppeteer](https://github.com/GoogleChrome/puppeteer) so you can navigate between multiple routes and assert on side effects not just in the browser, but potentially on the backend as well.