The `hide` action was calling the `block` method while the `soft_block`
action was calling the `hide` method.
Combined with the fact that we also have a `block` permission which is
used in `ModerateActions` the logic was hard to follow.
Other than removing a redundant action, we're fixing two bugs when
blocking an author using the links in the public views:
* We were always redirecting to the debates index, even if we blocked
the author of a proposal or an investment
* We weren't showing any kind of success message
I'm doing this in preparation for the "Manager" ability, which will
require even more refactors of the abilities (for example,
manager can not modify their own account)
