Fix numbered headings for Western Arabic (#16425)
Discussed here: https://groups.io/g/nvda-translations/message/3819
Summary of the issue:
In 2023.2, the user guide heading numbering for the Arabic translation switched to using Western Arabic numbering.
2024.1 mistakenly switched this back to Eastern Arabic numbering.
Description of user facing changes
Restore Western Arabic numbering style for headings.
Description of development approach
Updated CSS to reflect Western Arabic numbering style i.e. .1.2.3, .1.2.4
