Fix: Adjust PanelButtons spacing and alignment

[anshuksi282-ksolves]

Fix mis-aligned padding for Graph View options buttons

Issue #56076

Description:
This PR fixes the mis-aligned padding for the Graph View options buttons in the Airflow Web UI (3.1.0rc2).

Background:
The buttons on the upper-right (and slightly on the upper-left) of the Graph View were overlapping with the splitter due to inconsistent padding.
Although this issue was previously assigned to another contributor @alisha-malik, no PR has been submitted in the past 2 weeks. I started working on it now to resolve the open UI bug.

What this PR does:

• Corrects the padding for Graph View option buttons to ensure consistent alignment on all sides.
• Prevents the buttons from overlapping with the splitter in both left and right positions.

Notes:

• Minor UI fix; does not affect core functionality.
• Before

• After

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