theming: Revert broken SVG optimization in default-source.svg

[provokateurin]

Summary

f2afccf did some optimizations which inlined the included jpgs into the svg. This will make the image no longer update when the jpg files are updated and also bloats the svg itself. I'm pretty sure this was not intended.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[provokateurin]

/backport to stable27

[nickvergessen]

The next automatic run will bring this back. So the script at https://github.com/nextcloud/server/blob/master/build/image-optimization.sh needs adjusting I guess (could start with ignoring the file for now, future step find a parameter that skips "embedding")

[provokateurin]

Looking at the other "optinizations" it doesn't seem usefule to have that script. Changing the order of xml element attributes does nothing at all.