Bug#1101369: gocryptfs should depend on fuse3 package

[VA]

Package: gocryptfs
Version: 2.5.1-1

If fuse3 package isn't installed, gocryptfs fails with this error:
```
root@host:/# gocryptfs /test/ /mnt/
Password:
Decrypting master key
fs.Mount failed: exec: "/bin/fusermount": stat /bin/fusermount: no such 
file or directory
```

Currently, it's only a "recommends", but it's really a "depends" as 
gocryptfs is unusable without it.