### Please describe the problem.
borg special remote is apparently ignoring WORM and URL key content (probably all content without hashes?)

### What steps will reproduce the problem?
archive a repo containing WORM or URL keys with borg and sync it with git annex like in the example https://git-annex.branchable.com/special_remotes/borg/

doing `git annex list --not -i borg` later shows all WORM and URL keys not recognized being in borg

### What version of git-annex are you using? On what operating system?
git-annex version: 8.20210310
on NixOS 20.09

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)
Thank you for including borg, and for fixing gcrypt remotes! This is great!

> [[fixed|done]] --[[Joey]]
