Michael Baudino d752240efc Fix a configuration example in gantt.md
According to the [config schema docs](https://mermaid.js.org/config/schema-docs/config-defs-gantt-diagram-config.html#tickinterval-constraints), Gantt's `tickInterval` configuration must match the following regular expression, which does **not** allow any space:

```regexp
/^([1-9][0-9]*)(millisecond|second|minute|hour|day|week|month)$/
```
2024-10-29 13:09:54 +01:00
..