[Doc] fix possible values for securable_type in `databricks_workspa…

…ce_binding` (#3942)

## Changes
<!-- Summary of your changes that are easy to understand -->

Resolves #3941 

## Tests
<!-- 
How is this tested? Please see the checklist below and also describe any
other relevant tests
-->

- [ ] `make test` run locally
- [x] relevant change in `docs/` folder
- [ ] covered with integration tests in `internal/acceptance`
- [ ] relevant acceptance tests are passing
- [ ] using Go SDK

docs/resources/workspace_binding.md

@@ -35,7 +35,7 @@ The following arguments are required:
 
 * `workspace_id` - ID of the workspace. Change forces creation of a new resource.
 * `securable_name` - Name of securable. Change forces creation of a new resource.
-* `securable_type` - Type of securable. Can be `catalog`, `external_location` or `storage_credential`. Default to `catalog`. Change forces creation of a new resource.
+* `securable_type` - Type of securable. Can be `catalog`, `external-location` or `storage-credential`. Default to `catalog`. Change forces creation of a new resource.
 * `binding_type` - (Optional) Binding mode. Default to `BINDING_TYPE_READ_WRITE`. Possible values are `BINDING_TYPE_READ_ONLY`, `BINDING_TYPE_READ_WRITE`.
 
 ## Import