fix: correct SVG background

[Lorenzofg]

Problem

The current SVG icon has rendering issues when running as Flatpak on KDE
due to incorrect background settings, causing display errors in the SVG
interpreter.

Solution

Updated the icon background attributes to ensure proper rendering in KDE's
Flatpak environment.

Changes

• Modified: data/icons/com.github.marhkb.Pods.svg
• Fixed background attributes for proper SVG rendering on KDE

[marhkb]

Hi, I would like to merge this, but I don't fully understand what exactly the problem is and how this PR addresses it:

• What do you mean by "rendered not correctly"? A screenshot would definitely help here.
• What exactly was changed in the SVG (which background attributes were modified)?
• Why was the canvas size increased to 300px?

It would be great if this could also be documented in the commit message. Thanks!