make days abbreviation like the native gnome calendar ones

[burawi]

This PR aims to make the days' abbreviations like the ones in the native gnome calendar.

[omid]

Do you have any reference for this? I do not speak Arabic. But need a proof that they are how they call them.

[burawi]

Hey @omid Here is a screenshot from my gnome calendar in Arabic:

[omid]

Hey @burawi No no, I meant a wikipedia page or something, to show that abbr of weekdays in Arabic are so.

[nassimmiled]

@omid check this link from Microsoft, shows the abbr of weekdays in Arabic

[omid]

Thanks @nassimmiled So based on this, what we had was correct, and this PR should be rejected.