Invalid type for `cluster.routing.allocation.enable` in `elasticsearch_cluster_settings` resource

According to [documetation](https://www.elastic.co/guide/en/elasticsearch/reference/7.17/modules-cluster.html#cluster-shard-allocation-settings) `cluster.routing.allocation.enable` setting can have multiple values, but the provider is treating it as a bool value and generating errors
```
Error: strconv.ParseBool: parsing "all": invalid syntax
```
