Added comment to address A-Style Autoformatter

[ghost]

Addresses issue #5012 which discusses auto format and preferences.txt. This will help others find the correct file to edit for A-Style.

[matthijskooijman]

Sounds like a good addition. However, you now write "DO NOT CHANGE THIS FILE if you want to edit autoformatter", which suggests that preferences.txt contains autoformatter settings, but you shouldn't change them. Rather, I think that preferences.txt does not contain such settings, and it might be better to write something like "This file does not contain autoformatter settings. Instead... " etc.

If you want to update this PR, note that you can amend your commit and do a force push to replace the current contents of this PR, there is no need to create a new PR.

[ghost]

Thank you for your suggestion! I have edited the file with the altered message. Is there anything else I should do?

[matthijskooijman]

Looks good, thanks.

It might be good to squash these two changes in a single commit, though that can also be done by @facchinm or @cmaglie when merging the PR.