SlackPublisher Error logs secret

### Current Behavior:

When Slack notifications exceed the allowed Rate Limit, the following is logged:

```
10:51:55.724 ERROR [SlackPublisher] An error was encountered publishing notification to Slack
10:51:55.725 ERROR [SlackPublisher] HTTP Status : 429 Too Many Requests
10:51:55.725 ERROR [SlackPublisher] Destination: https://hooks.slack.com/services/XXXXXXXXX/YYYYYYYYY/ZZZZZZZZZZZZZZZZZZZZZZZZ
```
That's not the actual URL. I obfuscated it. DT actually logs the full URL

From [Slack Webhooks Documentation](https://api.slack.com/messaging/webhooks)

> Keep it secret, keep it safe. Your webhook URL contains a secret. Don't share it....

Logging = sharing! A lot of people in my company can view our DT logs.

### Steps to Reproduce:

See #1159

### Expected Behavior:

The logging should be tweaked so that the Slack Notification is uniquely identifiable... but not using the webhook URL.

### Environment:

- Dependency-Track Version: 4.3.1
- Distribution: [ Docker ]
- BOM Format & Version: CycloneDX 1.2
- Database Server: [PostgreSQL ]
- Browser: Firefox

### Additional Details:

Logging this one separately to #1159 as I am hoping that it should be quick and easy to address.

Start by locating the SlackPublisher implementation and inspect the error logging shown in the issue, using #1159 for reproduction context. The change is complete when Slack rate-limit errors remain identifiable without logging the Slack webhook URL or its secret.

Written by the indexing model from the issue text.