Wrong serialization of strings containing commas in flow style list

### Code

```kt
val list = listOf("foo", "bar, baz")
Yaml { listSerialization = YamlBuilder.ListSerialization.FLOW_SEQUENCE }.encodeToString(list)
```

### Expected

```yaml
[ foo, 'bar, baz' ]
```

### Actual

```yaml
[ foo, bar, baz ]
```

YamlKt version 0.13.0.