This change is to update the example docs for `host_set_plugin` filters attribute to use a list strings instead of just strings. WIthout using a list of strings, Terraform will falsely detect diffs with host set plugin `filters`. AWS host set plugin expects filters attributes to be passed as a list of strings instead of strings. It is currently backwards compatible with strings due to the migration [normalizeData func](https://github.com/hashicorp/boundary-plugin-aws/blob/7bf9fe2ecf1f20d7ff8aea8306909abcde1d17a4/plugin/service/host/plugin.go#L256) on AWS host plugin. Previously this was not working but [Boundary PR-3338](https://github.com/hashicorp/boundary/pull/3338) fixed the bug.