Replaced old logo with newer one.

[ElectronicsArchiver]

Fixes this horrible mess:

Preview: https://github.com/ElectronicsArchiver/MarlinDocumentation

[thinkyhead]

Thanks! Cleaned up and merged directly.

[ElectronicsArchiver]

@thinkyhead Oh right, forgot to enable edit permission.

Though I'm slightly confused, why do you need it in the first place and how did you merge it directly but close the PR itself?