Added a note on read-only property's setters (#3287)
Added a note on read-only property's setters (#3287)

* Added a note on read-only property setters

* re-wrote the part of the setter

* looked at the Swift protocol explanation

* fixed Obj-C name

* made things more laconic

JetBrains/kotlin-native,JetBrains/kotlin-native,JetBrains/kotlin-native,JetBrains/kotlin-native,wiltonlazary/kotlin-native,JetBrains/kotlin-native,JetBrains/kotlin-native,wiltonlazary/kotlin-native,JetBrains/kotlin-native,wiltonlazary/kotlin-native,JetBrains/kotlin-native,wiltonlazary/kotlin-native,JetBrains/kotlin-native,wiltonlazary/kotlin-native