Cleaned Up Filters in Antenna

I've said that custom filters that aren't used in three months will be removed, but I haven't actually removed any until now.

247 filters remain. Most of them had suffered from a bug that appeared for a brief period some months ago that would add all feeds on a single line without any delimiting character at the bottom of the file. I've removed all those now with the following command:

for filter in customfilters/*; do
    sed 's/gemini:.*gemini:.*//g' -i $filter
done

This malformed line didn't actually make a difference that I know of, except making every file multiple times bigger than needed. If you're using a filter I suggest you check that it still does what you want, and please forgive me if this quick purge caused any issues.

-- CC0 ew0k, 2022-03-06