Fixes FE-4107.
## What is the current behavior?
The Observability sidebar had unnecessary spacing below the Product
navigation.
- Extra whitespace below the last Product menu item (`Realtime`).
## What is the new behavior?
Removes the global flex gap and applies spacing explicitly to the Custom
Reports section.
- Product navigation ends cleanly at the divider.
- Spacing before the Custom Reports section is intentional and
consistent.
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
* **Style**
* Improved spacing and alignment in the observability menu.
* Added vertical separation around the custom reports section for a
cleaner layout.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Monica Khoury
a515f3d81f