[TASK] Update extension configuration of saltedpasswords

Saltedpasswords is using user functions in the ext_conf_template which
use type hinting for the config object. As the new extension manager
handles the rendering of the configuration form differently, the type
hints have to be removed.

Change-Id: I00abd45523ca833799bb3101cdc8262e977750a1
Resolves: #39935
Releases: 6.0
Reviewed-on: http://review.typo3.org/13901
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn