Log Message:
Update to 9.1.6

From the projects's announcement:

You'll find below the changes of this bugfixes version:

- various security fixes (#2475, #2476, #2492),
- fix regressions on self service portal:
  - self-service users should not be auto assigned as tech (#2472)
  - type and category fields was not selectable anymore (#2473)

The full changelog is available here for more details: \ 
https://github.com/glpi-project/glpi/milestone/20?closed=1