Remove Add-on Updater l10n exchange instructions from mrconfig

[josephsl]

Hi,

With the introduction of NV Access add-on store in late 2023, deep maintenance mode wsa declared for Add-on Updater. This means no new features - only critical bug fixes to respond to NVDA development and exchanging localization data. The work on the add-on store continued throughout 2024, incorporating more ideas from Add-on Updater such as add-on update notification. This has accellerated in 2025 with features such as changing update URL's and changing add-on update channels, with automatic add-on update process in the work (as of February 2025).

With rapid changes to add-on store feature with features coming from Add-on Updater, it makes more sense to discontinue the add-on altogether, and as part of this, I propose terminating localization exchange for Add-on Updater from mrconfig effective March 1, 2025 (so the final localization exchange would take place on February 28, 2025). This change would close #128 - we may not konw why l10n files are placed in odd locations, but given what's happening with the add-on store, I think it woul be better to say goodbye to Add-on Updater from mrconfig.

Thanks.