Broken references in Generic Sensor API

[dontcallmedom-bot]

While crawling Generic Sensor API, the following links to other specifications were detected as pointing to non-existing anchors:

• https://w3c.github.io/webdriver/#dfn-session
• https://w3c.github.io/webdriver/#dfn-url-variables

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

[rakuco]

Looks like we need to adapt to w3c/webdriver#1608.