FIR: relax simple type requirement in AbstractTypeMapper

The counterparts in old FE don't have such restriction, so it can
map a type that has a flexible type as a type argument to JVM type,
e.g., Stream<String..String?>

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/IrTypeMapper.kt

@@ -133,8 +133,8 @@ class IrTypeMapper(private val context: JvmBackendContext) : KotlinTypeMapperBas
         sw: JvmSignatureWriter? = null
     ): Type = AbstractTypeMapper.mapType(this, type, mode, sw)
 
-    override fun JvmSignatureWriter.writeGenericType(type: SimpleTypeMarker, asmType: Type, mode: TypeMappingMode) {
-        require(type is IrSimpleType)
+    override fun JvmSignatureWriter.writeGenericType(type: KotlinTypeMarker, asmType: Type, mode: TypeMappingMode) {
+        if (type !is IrSimpleType) return
         if (skipGenericSignature() || hasNothingInNonContravariantPosition(type) || type.arguments.isEmpty() || type.isRawTypeImpl()) {
             writeAsmType(asmType)
             return