The trailing `'` was included by mistake and is not supposed
to be there:
```ShellSession
$ base64 -w0 /etc/ssh/ssh_host_ed25519_key.pub
c3NoLWVkMjU1MTkgQUFBQUMzTnphQzFsWkRJMU5URTVBQUFBSUpCV2N4Yi9CbGFxdDFhdU90RStGOFFVV3JVb3RpQzVxQkorVXVFV2RWQ2Igcm9vdEBuaXhvcwo=
```
The reason it did not cause issues before is because
Nix ignores everything after the `=`:
3dbf9b5af5/src/libutil/util.cc (L1539-L1540)
… so it's harmless but still worth fixing.
930b0dfbc1