Add permission for get workflow step (opensearch-project#3937)

Description

Adds permission for a new Get Workflow Step API.
opensearch-project/flow-framework#394


### Check List
- [ ] New functionality includes testing
- [ ] New functionality has been documented
- [ ] Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and
signing off your commits, please check
[here](https://github.com/opensearch-project/OpenSearch/blob/main/CONTRIBUTING.md#developer-certificate-of-origin).

Signed-off-by: owaiskazi19 <[email protected]>

config/roles.yml

@@ -396,3 +396,4 @@ flow_framework_read_access:
     - 'cluster:admin/opensearch/flow_framework/workflow/search'
     - 'cluster:admin/opensearch/flow_framework/workflow_state/get'
     - 'cluster:admin/opensearch/flow_framework/workflow_state/search'
+    - 'cluster:admin/opensearch/flow_framework/workflow_step/get'