[FIR] Don't miss modality of anonymous objects in canHaveSubtypes()

They are not `FirRegularClassSymbol`, but are
final. `FirClassSymbol` is enough, because
`toSymbol()` returns `FirClassifierSymbol`, and:

- type parameters are always expected to have
  subtypes
- typealiases have been expanded in the
  previous line

compiler/fir/providers/src/org/jetbrains/kotlin/fir/types/TypeUtils.kt

@@ -592,7 +592,7 @@ fun ConeKotlinType.canHaveSubtypes(session: FirSession): Boolean {
         return true
     }
     val expandedType = fullyExpandedType(session)
-    val classSymbol = expandedType.toSymbol(session) as? FirRegularClassSymbol ?: return true
+    val classSymbol = expandedType.toSymbol(session) as? FirClassSymbol ?: return true
     // In K2 enum classes are final, though enum entries are their subclasses (which is a compiler implementation detail).
     if (classSymbol.isEnumClass || classSymbol.isExpect || classSymbol.modality != Modality.FINAL) {
         return true