Grafana plugin can't connect because describeQuery always throws an exception

I get this error in Grafana when it tries to connect to TimeBaseWS when viewing either of the [dashboard examples](https://github.com/epam/TimeBaseGrafanaPlugin/tree/main/dashboards) from the plugin repo.

```
Version 5.5 required
Object
status:500
statusText:"Internal Server Error"
data:Object
timestamp:"2021-12-15T18:01:15.898+0000"
status:500
error:"Internal Server Error"
message:"Version 5.5 required"
path:"/api/v0/describe"
config:Object
url:"api/datasources/proxy/1/api/v0/describe"
method:"POST"
headers:Object
Content-Type:"application/json"
X-Grafana-Org-Id:1
showSuccessAlert:false
showErrorAlert:false
data:Object
query:"select s.key as 'key', s.description as 'description', s.topTypes.name as 'topTypes' array join streams() as 's'"
retry:0
hideFromInspector:false
message:"Version 5.5 required"
```

I only see that error message when an exception is thrown in [`describeQuery`](https://github.com/epam/TimebaseWS/blob/4e9fcc9216a237975022796272bf77c5ed188e9e/java/ws-server/src/main/java/com/epam/deltix/tbwg/services/timebase/TimebaseServiceImpl.java#L188), and the method always and only throws that exception.

I'm running TimeBaseWS v0.5.15-SNAPSHOT and Grafana v8.3.3 (30bb7a93ca)