Fix Paste when SVG Mode is set to "new"

Regression introduced in bb714eb2 MR !6390 (merged)

We ensure that the import mode is set to "embed" even if it was set to "new" by the user when importing svgs previously.

This is NOT the fix I would have liked to do, but a full fix involves refactoring the file_import and making sure we can strip out the duplicate prefs (extension prefs vs. inkscape prefs) as well as removing the use of prefs used as state args.

Description:

1. Drag and drop an SVG file onto inkscape
2. Set the option to "open as a new document"
3. copy a screenshot onto the clipboard
4. Paste into inkscape

What happened:

• It made a new document for the screenshot

What should have happened:

• It should have pasted the screenshot into the existing document