[Fix] Fix Permissions Dashboard Test (#4071)

## Changes
<!-- Summary of your changes that are easy to understand -->
It seems like we need to specify the `serialized_dashboard` field to be
able to create the dashboard. I have raised this concern with the
responsible team. But for unblocking our integration tests we can
specify this for now.

## Tests
<!-- 
How is this tested? Please see the checklist below and also describe any
other relevant tests
-->
Integration Tests Passing
- [x] `make test` run locally
- [x] covered with integration tests in `internal/acceptance`
- [x] relevant acceptance tests are passing

Author: parthban-db

internal/acceptance/permissions_test.go

@@ -722,6 +722,7 @@ func TestAccPermissions_Dashboard(t *testing.T) {
 			display_name = "TF New Dashboard"
 			warehouse_id = "{env.TEST_DEFAULT_WAREHOUSE_ID}"
 			parent_path = databricks_directory.this.path
+			serialized_dashboard = "{\"pages\":[{\"name\":\"b532570b\",\"displayName\":\"New Page\"}]}"
 		}
 		`
 	WorkspaceLevel(t, Step{