[FIR] Replace FirExpression.typeRef.coneType (and variants) with FirExpression.coneType

#KT-59855

plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/checkers/FirSerializationPluginClassChecker.kt

@@ -175,8 +175,8 @@ object FirSerializationPluginClassChecker : FirClassChecker() {
             this is FirConstExpression<*> && other is FirConstExpression<*> -> kind == other.kind && value == other.value
             this is FirGetClassCall && other is FirGetClassCall -> AbstractTypeChecker.equalTypes(
                 session.typeContext,
-                typeRef.coneType,
-                other.typeRef.coneType
+                coneType,
+                other.coneType
             )
 
             this is FirPropertyAccessExpression && other is FirPropertyAccessExpression ->