Remove dead SVG style parser wrappers

[rowland]

Summary

• Removed the unused parseStyleSpec wrapper from svg/parse.go.
• Confirmed mergeStyleSpec was also dead and already deleted.
• Kept the font-family parsing and SVG fallback logic intact.

Testing

• Ran focused validation for svg, pdf, and ttf_fonts.
• Verified no remaining references to parseStyleSpec or mergeStyleSpec in the repo.