Remove instances of `ActionController::Parameters#to_unsafe_h`

[cbeer]

We'll want to provide something downstream so applications (and plugins) can allow-list expected search parameters.

[barmintor]

@cbeer do you still feel like this needs to be in 7.0?

[barmintor]

Marking as 7.x, since the allowlist configuration would be a new feature.

[carolyncole]

There are only two instances: https://github.com/projectblacklight/blacklight/search?q=to_unsafe_h