The GRUB menu editing approach is fragile because:
1. GRUB can auto-boot before the test interacts with the menu
2. The command line content varies (e.g. '$vt_handoff' vs 'quiet splash')
3. Character-by-character navigation depends on exact screen layout
Simplify to just verify that EFI boot through GRUB reaches Linux
userspace, without trying to edit the kernel command line.
Co-developed-by: Claude <noreply@anthropic.com>
Signed-off-by: Simon Glass <simon.glass@canonical.com>
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