Documentation: ACPI: fix error script name

The correct script name should be 'divergence.sh' instead of
'divergences.sh'.
I didn't find divergences.sh in the path of acpica/generate/linux/.

Signed-off-by: Hao Chen <chenhaoa@uniontech.com>
Link: https://lore.kernel.org/r/20210617023300.30114-1-chenhaoa@uniontech.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>