test(ui5-menu): re-enable flaky 'Add endContent to a menu item' test

[nnaydenow]

The following test was temporarily skipped in #13656 due to flakiness on CI:

• File: packages/main/cypress/specs/Menu.cy.tsx
• Test: Add endContent to a menu item
• Error: Timed out retrying after 4000ms: expected '<ui5-menu#menu>' to have attribute 'open'

[GDamyanov]

Hello @UI5/ui5-team-ctr-bal,

Could you check this skipped?

Kind Regards,
Georgi