tools/privacyidea-token-janitor: fix options examples
tools/privacyidea-token-janitor: fix options examples

* The `--orphaned`-option expects a boolean option, otherwise it fails
  like this:

  ```
  privacyidea-token-janitor find: error: argument --orphaned: expected one argument
  ```

* The `--unassigned` option doesn't exist, instead `--assigned false`
  has to be provided.

privacyidea/privacyidea,privacyidea/privacyidea,privacyidea/privacyidea,privacyidea/privacyidea,privacyidea/privacyidea,privacyidea/privacyidea