main/hunspell-en-au: use correct dictionary
Given that upstream provides an actual dictionary for en_AU, it seems wrong that we just install a symlink to en_GB.
We are currently working on getting Alpine Linux 3.21 out. This means that merge requests that are not aimed to help with that (only affecting testing, new aports) have a lower priority at the moment. Please be patient, they will be eventually picked up.
Given that upstream provides an actual dictionary for en_AU, it seems wrong that we just install a symlink to en_GB.