Updating "system requirements" page on LibreOffice websites

l10n
#1

Hello everyone,

This is about the system requirements for macOS:

https://www.libreoffice.org/get-help/system-requirements/#Apple

They should be:

* LibreOffice 6.3.x: macOS 10.10 (Yosemite) or higher
* LibreOffice 6.2.x: macOS 10.9 (Mavericks) or higher

Someone pointed out that the English version had a mistake, and some
other pages didn't show the difference between LO 6.2 and 6.3. So I've
fixed some of the pages I can (kinda) understand: English, German,
French, Italian, Spanish and Slovene.

But for all other maintainers of native language sites, if you can
please check the system requirements page and ensure it matches the
details above, that'd be great, thanks! :slight_smile: