Add delete /tmp directory after backup or restore and update docs

docs/how-tos/encrypt-backup.md

@@ -11,7 +11,7 @@ The image supports encrypting backups using GPG out of the box. In case a `GPG_P
 {: .warning }
 To restore an encrypted backup, you need to provide the same GPG passphrase used during backup process.
 
-To decrypt manually, you need to install gnupg
+To decrypt manually, you need to install `gnupg`
 
 ### Decrypt backup