K1 allows writing access to a public setter of a protected synthetic
property only if the call is inside a subclass. K2 previously allowed
that unconditionally. This changes brings the behavior in line with K1.
^KT-56050 Fixed
Assuming Java class `Super` has a protected `getName` method and a
public `setName` method.
Then, in a subclass of `Super`, FE1.0 allows calls to `setName` via the
property syntax if the property is protected and invisible due to
dispatch receiver is not `this` or `super`.
Kirill Rakhman