Cleanup: drop unused ExpectActualCompatibility.Incompatible.Unknown

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/ClassicPositioningStrategies.kt

@@ -49,7 +49,7 @@ object ClassicPositioningStrategies {
                 val callableDeclaration = element as? KtCallableDeclaration
                 val incompatibility = diagnostic.firstIncompatibility
                 return when (incompatibility) {
-                    null, ExpectActualCompatibility.Incompatible.Unknown, is ExpectActualCompatibility.Incompatible.ClassScopes,
+                    null, is ExpectActualCompatibility.Incompatible.ClassScopes,
                     ExpectActualCompatibility.Incompatible.EnumEntries -> null
                     ExpectActualCompatibility.Incompatible.ClassKind -> {
                         val startElement =

core/compiler.common/src/org/jetbrains/kotlin/resolve/multiplatform/ExpectActualCompatibility.kt

@@ -94,8 +94,6 @@ sealed class ExpectActualCompatibility<out D> {
         object TypeParameterReified : WeakIncompatible<Nothing>(
             "some type parameter is reified in one declaration and non-reified in the other"
         )
-
-        object Unknown : WeakIncompatible<Nothing>(null)
     }
 
     object Compatible : ExpectActualCompatibility<Nothing>()

core/compiler.common/src/org/jetbrains/kotlin/resolve/multiplatform/ExpectActualMemberDiff.kt

@@ -86,7 +86,6 @@ private fun ExpectActualCompatibility.Incompatible<*>.toDiffKind(): ExpectActual
     ExpectActualCompatibility.Incompatible.TypeParameterNames -> ExpectActualMemberDiff.Kind.TypeParameterNamesChangedInOverride
     ExpectActualCompatibility.Incompatible.TypeParameterReified -> null // inline fun can't be overridden
     ExpectActualCompatibility.Incompatible.TypeParameterVariance -> null // Members are not allowed to have variance
-    ExpectActualCompatibility.Incompatible.Unknown -> null // Unknown incompatibility is never reported
     ExpectActualCompatibility.Incompatible.ValueParameterCrossinline -> null // inline fun can't be overridden
     ExpectActualCompatibility.Incompatible.ValueParameterNoinline -> null // inline fun can't be overridden
     ExpectActualCompatibility.Incompatible.ValueParameterVararg -> ExpectActualMemberDiff.Kind.NonPrivateCallableAdded