Dashboard: invalid time interval when max data point is one

### What happened? When I set "max data point" to "1", and use a time range of 6 days, I got an interval of 1d Despite the formula mentioning "time range / max data point" (6 days / 1) <img width="1528" alt="image" src="https://github.com/grafana/grafana/assets/5497623/211550b3-8002-4326-a060-4353950f11b1"> ### What did you expect to happen? The interval to follow the selected time range ### Did this work before? I don't know ### How do we reproduce it? 1. new dashboard, new panel 2. time range now / now-6d 3. max data point -> 1 ### Is the bug inside a dashboard panel? _No response_ ### Environment (with versions)? **Grafana**: 9.5.5 **OS**: MacOS 13.4.1 (22F82) **Browser**: Chrome 114.0.5735.133 (Official build) (arm64) ### Grafana platform? Kubernetes ### Datasource(s)? _No response_