feat(connectHitsPerPage): clear the state on dispose (#3818)

* test(connectHitsPerPage): calls the unmount function

* test(connectHitsPerPage): rename jsHelper -> algoliasearchHelper

* test(connectHitsPerPage): consistent names for render/unmount function

* feat(connectHitsPerPage): remove hitsPerPage on dispose

* feat(connectHitsPerpage): do not throw without unmount function

Author: samouss