Update e2e tests from upstream repository. (#24708)

Ideally, we'd eventually have a single source of truth for these.

e2e-tests/cypress/tests/integration/playbooks/channels/rhs/checklist_spec.js

@@ -164,7 +164,7 @@ describe('channels > rhs > checklist', {testIsolation: true}, () => {
             });
 
             // * Verify the expected error message.
-            cy.verifyEphemeralMessage('Failed to find slash command /invalid');
+            cy.verifyEphemeralMessage('Failed to execute slash command /invalid');
         });
 
         it('successfully runs a valid slash command', () => {