Remove "Safe mode" check for Coercible instances

We assume that library authors supply correct role annotations
for their types, and therefore we do not need to check for
the availability of data constructors in Safe mode. See
discussion in #8725. This effectively fixes #8827 and #8826.
Recharacterize test according to discussion in #8851.
Fix #8884.

There were two unrelated errors fixed here:
 1) Make sure that only the *result kind* is reified when reifying
    a type family. Previously, the whole kind was reified, which
    defies the TH spec.

 2) Omit kind patterns in equations.
Fix typo in user's manual, changing "-j N" to "-jN".