defaults : switch prefix and suffix

I mixed up the prefix and suffix, fix that

src/unisync/defaults.py

@@ -21,5 +21,5 @@ DEFAULT_BACKUP_ENABLED: bool = False
 DEFAULT_BACKUP_SELECTION: str = ""
 DEFAULT_BACKUP_LOC: str = "local"
 DEFAULT_BACKUP_MAX_BACKUPS: int = 2
-DEFAULT_BACKUP_BACKUPSUFFIX: str = ".unison_backups/"
-DEFAULT_BACKUP_BACKUPPREFIX: str = ".$VERSION.bak"
+DEFAULT_BACKUP_BACKUPSUFFIX: str = ".$VERSION.bak"
+DEFAULT_BACKUP_BACKUPPREFIX: str = ".unison_backups/"