Set users_forbid_delegator_to_vote default to true

[Elblinator]

Explanation:
The new field from this PR (#2370) added a new setting for delegations and a more refined behaviour.

Wanted behaviour:*
The new default is not the same as the old default to prevent this new unintended behaviour the setting (users_forbid_delegator_to_vote) should be set to true per default

[rrenkert]

This one is obsolete. We want to keep the default "false" (no value set).