K-9 (com.fsck.k9) is outdated (5.740 -> 5.800)

A new K-9 version was released a while ago and the author did at least something to get it released in F-Droid, but it is still not available:

• https://forum.k9mail.app/t/k-9-mail-is-back-5-800-release/1164/3
• !9435 (merged)
• https://f-droid.org/wiki/page/com.fsck.k9/lastbuild_28000