chore(cypress): migrate to Cypress v6 (#40396)

* Update Cypress version from 5.3.0 to 6.0.0

* Replace `not.be.visible` with `not.exist`

Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>

cypress/integration/landing.js

@@ -60,7 +60,7 @@ describe('Landing page', () => {
 
     cy.viewport(1199, 660)
       .get(selectors.landingPageImage)
-      .should('not.be.visible');
+      .should('not.exist');
   });
 
   it('Has links to all the certifications', function() {