VM has different responses to equivalent queries for MetricsQL and
GraphiteQL in case of failed access to one of vmstorage node of the
cluster vmstorage nodes. For GraphiteQL, the denyPartialResponse feature
is not used, it is always true, which is not always correct (depending
on the configuration).
In the PR I have removed the hardcoded denyPartialResponse for
GraphiteQL, just like MetricsQL does.
- [x] My change adheres [VictoriaMetrics contributing
guidelines](https://docs.victoriametrics.com/contributing/).