Align to Cypress default template spec

[MikeMcC399]

Closes https://github.com/cypress-io/cypress-realworld-testing-course-app/issues/26

This PR updates Testing Your First Application > Installing Cypress and writing your first test.

The Cypress default template derives from empty.ejs which uses a describe text 'template spec' and single quotes:

---
fileName: <%= fileName %>
---

describe('template spec', () => {
  it('passes', () => {
    cy.visit('https://example.cypress.io')
  })

The text is changed in the training materials to match the default template text 'template spec' from Cypress 12.14.0 and later.

The double quotes are left unchanged. These are used in too many places to want to change them.

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[MikeMcC399]

For consistency, the screenshot

https://github.com/cypress-io/cypress-realworld-testing/blob/main/public/images/testing-your-first-application/installing-cypress-and-writing-your-first-test/Screen_Shot_2022-06-28_at_9.03.44_AM.png

on the page

Testing Your First Application > Installing Cypress and writing your first test

would also need to be updated. It looks like this was done with macOS / Safari, which I don't have access to.

[MikeMcC399]

Closed due to lack of response.