Adjusted svg for firefox compatibility

[SusiJo]

PR checklist

This PR fixes the SVG issue of the subway map, in which weird lines were displayed in Firefox. SVGs that are produced with Adobe Illustrator add masks to the paths that cannot be processed by Firefox, therefore Inkscape is actually the better choice for SVG development across browsers.

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[FriederikeHanssen]

nice thank you. What was the trick?

[SusiJo]

Switching to Inkscape and changing everything again :D
The fonts in your previous version were not displayed because the objects were not actually text and needed to be converted to text