Update DAVx5 in AuthToken.vue

1. It's named DAVx5 (only very old clients have DAVdroid in the User-Agent)
2. Use passive matching (?:droid|x5) because otherwise, "x5" is recognized and shown as operating system
3. Also include the version postfix which contains information like "-beta2", which is important for the user

Signed-off-by: npmbuildbot-nextcloud[bot] <npmbuildbot-nextcloud[bot]@users.noreply.github.com>