Broken references in Layout Instability API

[dontcallmedom-bot]

While crawling Layout Instability API, the following links to other specifications were detected as pointing to non-existing anchors, which should be fixed:

• https://w3c.github.io/resource-timing/#sec-privacy-security
• https://www.w3.org/TR/css-values-4/#pixel-unit

_{This issue was detected and reported semi-automatically by Strudy based on data collected in webref.}