Reduce ERROR notifications for certain "normal" metadata scenarios (i.e. 404)

### Current Behavior

I noticed that every non 2xx http response code triggers an `ERROR` notification to be raised for metadata analysis:

https://github.com/DependencyTrack/dependency-track/blob/45982a2e1a12a0b0de17f955b856b27008fee02a/src/main/java/org/dependencytrack/tasks/repositories/AbstractMetaAnalyzer.java#L78-L89

### Proposed Behavior

I propose to make this less noisy. The logging is already on `DEBUG` level, maybe the notification should be on `DEBUG` as well. At least for `404` which can be quite normal, at least for the Composer Package Repository (#4470)
Maybe other `4xx` and `5xx` errors could/should trigger `WARN` or `ERROR`.

### Checklist

- [x] I have read and understand the [contributing guidelines](https://github.com/DependencyTrack/dependency-track/blob/master/CONTRIBUTING.md#filing-issues)
- [x] I have checked the [existing issues](https://github.com/DependencyTrack/dependency-track/issues) for whether this enhancement was already requested