Tutorial still references deprecated "Open Shell" tray option + old icons

**Multipass Tutorial is outdated**
The Multipass tutorial still contains screenshots and instructions referencing deprecated UI elements, particularly the “Open Shell” option in the tray menu. Some screenshots also show an outdated Multipass app icon.

**Proposal to fix issue or enact suggestion**
Update the remaining outdated screenshots to reflect the current Multipass UI, and update the accompanying instructions so they no longer direct users to select the deprecated “Open Shell” option.

**Additional context**
This was originally reported in #4610 and subsequently marked as resolved by #4775.

However, #4775 appears to have only partially addressed the issue: it updated some of the screenshots, but some outdated screenshots remain, and the tutorial text still references the deprecated “Open Shell” workflow.