Headings not aligned without addSectionLinks

[sanderke]

Description of problem

Setting addSectionLinks to false causes numbered headings to move slightly to the left.

https://w3c.github.io/payment-request/?addSectionLinks=false#examples-of-usage

https://w3c.github.io/payment-request/?addSectionLinks=true#examples-of-usage

What happened (e.g., it crashed)?:
Minor visual issue

Expected behavior (e.g., it shouldn't crash):

Expected same alignment with or without linked "§" section markers and same alignment for numbered and unnumbered headings.