Fix up for numbered headings for Western Arabic

[seanbudd]

Link to issue number:

Fixup of #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.
In #16425, the headers in the table of contents were fixed for Western Arabic, but not in the body.

Description of user facing changes

Restore Western Arabic numbering style for headings in the body of the document

Description of development approach

Updated CSS to reflect Western Arabic numbering style i.e. .1.2.3, .1.2.4

Testing strategy:

Compared:

• https://www.nvaccess.org/files/nvda/releases/2024.1/documentation/ar/userGuide.html
• https://www.nvaccess.org/files/nvda/releases/2023.3/documentation/ar/userGuide.html
• Checked generated Arabic and Persian documentation with new CSS: https://ci.appveyor.com/project/NVAccess/nvda/builds/49846213

Known issues with pull request:

None